Fluorine-containing block copolymeric compound

ABSTRACT

A fluorine-containing polymeric compound which contains a structural unit (f1) that is decomposable in an alkali developing solution as a block copolymer portion, a base component (A) that exhibits increased solubility in an alkali developing solution under the action of acid, and an acid generator component (B) that generates acid upon exposure.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/824,089, filed Jun. 25, 2010, which claims priority under 35 U.S.C.§119(a)-(d) to Japanese Patent Application No. 2009-159073, filed Jul.3, 2009, the content of which is incorporated herein by reference in itsentirety.

TECHNICAL FIELD

The present invention relates to a positive resist composition includinga fluorine-containing compound, a method of forming a resist patternusing the resist composition, and a fluorine-containing polymericcompound.

This Application

BACKGROUND ART

In lithography techniques, for example, a resist film composed of aresist material is formed on a substrate, and the resist film issubjected to selective exposure of radial rays such as light or electronbeam through a mask having a predetermined pattern, followed bydevelopment, thereby forming a resist pattern having a predeterminedshape on the resist film.

As shortening the wavelength of the exposure light source progresses, itis required to improve various lithography properties of the resistmaterial, such as the sensitivity to the exposure light source and aresolution capable of reproducing patterns of minute dimensions. As aresist material which satisfies these conditions, a chemically amplifiedresist is used, which includes a base resin that exhibits a changedsolubility in an alkali developing solution under action of acid and anacid generator that generates acid upon exposure.

Currently, resins that contain structural units derived from(meth)acrylate esters within the main chain (acrylic resins) are nowwidely used as base resins for chemically amplified resists that use ArFexcimer laser lithography, as they exhibit excellent transparency in thevicinity of 193 nm (for example, see Patent Document 1).

Here, the term “(meth)acrylic acid” is a generic term that includeseither or both of acrylic acid having a hydrogen atom bonded to theα-position and methacrylic acid having a methyl group bonded to theα-position. The term “(meth)acrylate ester” is a generic term thatincludes either or both of the acrylate ester having a hydrogen atombonded to the α-position and the methacrylate ester having a methylgroup bonded to the α-position. The term “(meth)acrylate” is a genericterm that includes either or both of the acrylate having a hydrogen atombonded to the α-position and the methacrylate having a methyl groupbonded to the α-position.

As a technique for further improving the resolution, a lithographymethod called liquid immersion lithography (hereafter, frequentlyreferred to as “immersion exposure”) is known in which exposure(immersion exposure) is conducted in a state where the region betweenthe lens and the resist layer formed on a wafer is filled with a solvent(a immersion medium) that has a larger refractive index than therefractive index of air (see for example, Non-Patent Document 1).

According to this type of immersion exposure, it is considered thathigher resolutions equivalent to those obtained using a shorterwavelength light source or a larger NA lens can be obtained using thesame exposure light source wavelength, with no lowering of the depth offocus. Furthermore, immersion exposure can be conducted using aconventional exposure apparatus. As a result, it is expected thatimmersion exposure will enable the formation of resist patterns ofhigher resolution and superior depth of focus at lower costs.Accordingly, in the production of semiconductor devices, which requiresenormous capital investment, immersion exposure is attractingconsiderable attention as a method that offers significant potential tothe semiconductor industry, both in terms of cost and in terms oflithography properties such as resolution.

Immersion lithography is effective in forming patterns having variousshapes. Further, immersion exposure is expected to be capable of beingused in combination with currently studied super-resolution techniques,such as phase shift method and modified illumination method. Currently,as the immersion exposure technique, technique using an ArF excimerlaser as an exposure source is being actively studied. Further, water ismainly used as the immersion medium.

In recent years, fluorine-containing compounds have been attractingattention for their properties such as water repellency andtransparency, and active research and development of fluorine-containingcompounds have been conducted in various fields.

For example, in the fields of resist materials, currently, anacid-labile group such as a methoxymethyl group, tert-butyl group ortert-butoxycarbonyl group is being introduced into a fluorine-containingpolymeric compound, and the fluorine-containing polymeric compound isused as a base resin for a chemically amplified positive resist.

However, when such a fluorine-containing polymeric compound is used as abase resin for a positive resist, disadvantages are caused in that alarge amount of an out gas is generated, and resistance to a dry-etchinggas (etching resistance) is unsatisfactory.

Recently, as a fluorine-containing polymeric compound exhibitingexcellent etching resistance, a fluorine-containing polymeric compoundhaving an acid-labile group containing a cyclic hydrocarbon group hasbeen reported (see, for example, Non-Patent Document 2).

In addition, a fluorine-containing polymeric compound has been reportedin order to provide a resist film with water repellency in a resistcomposition for immersion exposure (see, for example, Non-PatentDocument 3).

DOCUMENTS OF RELATED ART Patent Document

[Patent Document 1] Japanese Unexamined Patent Application, FirstPublication No. 2003-241385

Non-Patent Documents

[Non-Patent Document 1] Proceedings of SPIE (U.S.), vol. 5754, pp.119-128 (2005)

[Non-Patent Document 2] Proceedings of SPIE (U.S.), vol. 4690, pp. 76-83(2002)

[Non-Patent Document 3] Journal of Photopolymer.Sci.Technol., vol. 19,No. 4, pp. 565-568 (2006)

SUMMARY OF THE INVENTION

For example, in immersion exposure, a resist material is required whichexhibits not only general lithography properties (e.g., sensitivity,resolution, etching resistance and the like), but also properties suitedfor immersion lithography. In immersion exposure, when the resist filmcomes in contact with the immersion medium, elution of a substancecontained in the resist film into the immersion medium occurs. Thiselution of a substance causes phenomenon such as degeneration of theresist film and change in the refractive index of the immersion medium,thereby adversely affecting the lithography properties. The amount ofthe eluted substance is affected by the properties of the resist filmsurface (e.g., hydrophilicity, hydrophobicity, and the like). Forexample, by enhancing the hydrophobicity of the resist film surface, theelution of a substance can be reduced. Further, when the immersionmedium is water, and immersion exposure is performed using ascanning-type immersion exposure apparatus as disclosed in Non-PatentDocument 1, a water tracking ability in which the immersion medium iscapable of tracking the movement of the lens is required. When the watertracking ability is low, the exposure speed becomes low, and as aresult, there is a possibility that the productivity is adverselyaffected. It is presumed that the water tracking ability can be improvedby enhancing the hydrophobicity of the resist film (rendering the resistfilm hydrophobic).

Accordingly, it is presumed that the above-described characteristicproblems of immersion lithography, which require a reduction insubstance elution and an improvement in the water tracking ability, canbe addressed by enhancing the hydrophobicity of the resist film surface.However, if the resist film is simply rendered hydrophobic, then adverseeffects are seen on the lithography properties. For example, as thehydrophobicity of the resist film is increased, defects tend to occurmore readily on the surface of the formed resist pattern followingalkali developing. Especially, in the case of a positive resistcomposition, defects are likely to be generated at unexposed portions.

The term “defects” refers to general abnormalities within a resist filmthat are detected when observed from directly above the developed resistfilm using, for example, a surface defect detection apparatus (productname: “KLA”) manufactured by KLA-TENCOR Corporation. Examples of theseabnormalities include post-developing scum, foam, dust, bridges(structures that bridge different portions of the resist pattern), colorirregularities, and foreign deposits and residues. These defects areregarded as problems not only in immersion lithography, but also inother lithography techniques. It is presumed that the problem of defectscan be solved by a material which is capable of increasing thehydrophilicity of the resist film during development. However, such amaterial is essentially unknown in the art.

The present invention takes the above circumstances into consideration,with an object of providing a resist composition, a method of forming aresist pattern that uses the resist composition, and afluorine-containing polymeric compound that is useful as an additive forthe resist composition.

For solving the above-mentioned problems, the present invention employsthe following aspects.

Specifically, a first aspect of the present invention is a positiveresist composition including a fluorine-containing polymeric compound(F) which contains a structural unit (f1) that is decomposable in analkali developing solution as a block copolymer portion, a basecomponent (A) that exhibits increased solubility in an alkali developingsolution under the action of acid, and an acid generator component (B)that generates acid upon exposure.

A second aspect of the present invention is a method of forming a resistpattern including using a resist composition according to the firstaspect to form a resist film on a substrate, subjecting the resist filmto immersion exposure, and subjecting the resist film to alkalideveloping to form a resist pattern.

A third aspect of the present invention is a fluorine-containingpolymeric compound including a structural unit (f1) that is decomposablein an alkali developing solution as a block copolymer portion.

In the present description and claims, an “alkyl group” includes linear,branched or cyclic, monovalent saturated hydrocarbon, unless otherwisespecified.

The term “alkylene group” includes linear, branched or cyclic divalentsaturated hydrocarbon, unless otherwise specified.

A “halogenated alkyl group” is a group in which part or all of thehydrogen atoms of an alkyl group is substituted with a halogen atom.Examples of the halogen atom include a fluorine atom, a chlorine atom, abromine atom and an iodine atom.

The term “aliphatic” is a relative concept used in relation to the term“aromatic”, and defines a group or compound that has no aromaticity.

The term “structural unit” refers to a monomer unit that contributes tothe formation of a polymeric compound (polymer, copolymer).

The term “exposure” is used as a general concept that includesirradiation with any form of radiation.

According to the present invention, there are provided a resistcomposition preferable for improving defects during development andsuitable for use in immersion exposure, a method of forming a resistpattern that uses the resist composition, and a fluorine-containingcompound that is useful as an additive for the resist composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram of an advancing angle (θ1), a recedingangle (θ2) and a sliding angle (θ3).

MODE FOR CARRYING OUT THE INVENTION

The positive resist composition of the present invention includes a basecomponent (A) which exhibits changed solubility in an alkali developingsolution under action of acid (hereafter, referred to as “component(A)”), an acid-generator component (B) which generates acid uponexposure (hereafter, referred to as “component (B)”) and afluorine-containing polymeric compound (F) (hereafter, referred to as“component (F)”) which includes a structural unit (f1) that isdecomposable in an alkali developing solution as a block copolymerportion.

<Component (A)>

In the present invention, the term “base component” refers to an organiccompound capable of forming a film.

As the base component, an organic compound having a molecular weight of500 or more can be preferably used. When the organic compound has amolecular weight of 500 or more, the film-forming ability is improved,and a resist pattern of nano level can be easily formed.

The “organic compound having a molecular weight of 500 or more” whichcan be used as a base component is broadly classified into non-polymersand polymers.

In general, as a non-polymer, any of those which have a molecular weightin the range of 500 to less than 4,000 is used. Hereafter, a non-polymerhaving a molecular weight in the range of 500 to less than 4,000 isreferred to as a low molecular weight compound.

As a polymer, any of those which have a molecular weight of 1,000 ormore is generally used. Hereafter, a polymer having a molecular weightof 1,000 or more is referred to as a polymeric compound. With respect toa polymeric compound, the “molecular weight” is the weight averagemolecular weight in terms of the polystyrene equivalent value determinedby gel permeation chromatography (GPC). Hereafter, a polymeric compoundis frequently referred to simply as a “resin”.

In the present invention, the component (A) contains a polymericcompound (A1) (hereafter, referred to as “component (A1)”) including astructural unit (a1) derived from an acrylate ester containing an aciddissociable, dissolution inhibiting group.

[Component (A1)]

The component (A1) is a polymeric compound including the structural unit(a1).

Further, the component (A1) preferably includes a structural unit (a0)represented by general formula (a0-1), as well as the structural unit(a1).

Furthermore, it is preferable that the component (A1) include astructural unit (a3) derived from an acrylate ester containing a polargroup-containing aliphatic hydrocarbon group, as well as the structuralunit (a1), or the structural unit (a1) and the structural unit (a0).

The component (A1) may further include a structural unit (a2).

In formula (a0-1), R represents a hydrogen atom, an alkyl group of 1 to5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R⁰²represents a divalent linking group; and R⁰³ represents a cyclic groupcontaining an —SO₂— group within the ring skeleton thereof

(Structural Unit (a0))

In general formula (a0-1), R represents a hydrogen atom, an alkyl groupof 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbonatoms.

As the alkyl group for R, a linear or branched alkyl group of 1 to 5carbon atoms is preferable, and specific examples thereof include amethyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group and a neopentyl group.

The halogenated alkyl group for R is a group in which part or all of thehydrogen atoms of the aforementioned alkyl group has been substitutedwith halogen atoms. Examples of the halogen atom include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is particularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is particularly desirable in terms ofindustrial availability.

In general formula (a0-1), R⁰² represents a divalent linking group.Preferable examples of R⁰² include a divalent hydrocarbon group whichmay have a substituent, and a divalent linking group containing a heteroatom.

—Divalent Hydrocarbon Group which May have a Substituent

With respect to R⁰², the hydrocarbon group “has a substituent” meansthat part or all of the hydrogen atoms within the hydrocarbon group hasbeen substituted with a group or an atom other than a hydrogen atom.

The hydrocarbon group may be either an aliphatic hydrocarbon group or anaromatic hydrocarbon group. An “aliphatic hydrocarbon group” refers to ahydrocarbon group that has no aromaticity.

The aliphatic hydrocarbon group may be saturated or unsaturated. Ingeneral, the aliphatic hydrocarbon group is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

The linear or branched aliphatic hydrocarbon group preferably has 1 to10 carbon atoms, more preferably 1 to 8, still more preferably 1 to 5,and most preferably 1 or 2.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable. Specific examples thereof include a methylene group [—CH₂—],an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group (chain-like aliphatichydrocarbon group) may or may not have a substituent. Examples of thesubstituent include a fluorine atom, a fluorinated alkyl group of 1 to 5carbon atoms, and an oxygen atom (═O).

As examples of the hydrocarbon group containing a ring in the structurethereof, a cyclic aliphatic hydrocarbon group (a group in which twohydrogen atoms have been removed from an aliphatic hydrocarbon ring),and a group in which the cyclic aliphatic hydrocarbon group is bonded tothe terminal of the aforementioned chain-like aliphatic hydrocarbongroup or interposed within the aforementioned chain-like aliphatichydrocarbon group, can be given.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbonatoms, and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic groupor a monocyclic group.

As the monocyclic group, a group in which two hydrogen atoms have beenremoved from a monocycloalkane of 3 to 6 carbon atoms is preferable.Examples of the monocycloalkane include cyclopentane and cyclohexane.

As the polycyclic group, a group in which two hydrogen atoms have beenremoved from a polycycloalkane of 7 to 12 carbon atoms is preferable.Examples of the polycycloalkane include adamantane, norbornane,isobornane, tricyclodecane and tetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent.

Examples of the substituent include an alkyl group of 1 to 5 carbonatoms, a fluorine atom, a fluorinated alkyl group of 1 to 5 carbonatoms, and an oxygen atom (═O).

Examples of aromatic hydrocarbon groups include a divalent aromatichydrocarbon group in which one hydrogen atom has been removed from abenzene ring of a monovalent aromatic hydrocarbon group such as a phenylgroup, a biphenyl group, a fluorenyl group, a naphthyl group, an anthrylgroup or a phenanthryl group;

an aromatic hydrocarbon group in which part of the carbon atomsconstituting the ring of the aforementioned divalent aromatichydrocarbon group has been substituted with a hetero atom such as anoxygen atom, a sulfur atom or a nitrogen atom; and

and an aromatic hydrocarbon group in which one hydrogen atom has beenremoved from a benzene ring of an arylalkyl group such as a benzylgroup, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethylgroup, a 1-naphthylethyl group or a 2-naphthylethyl group.

The aromatic hydrocarbon group may or may not have a substituent.Examples of the substituent include an alkyl group of 1 to 5 carbonatoms, a fluorine atom, a fluorinated alkyl group of 1 to 5 carbonatoms, and an oxygen atom (═O).

—Divalent Linking Group Containing a Hetero Atom

With respect to the “divalent linking group containing a hetero atom”for R⁰², a hetero atom refers to an atom other than carbon and hydrogen,and examples thereof include an oxygen atom, a nitrogen atom, a sulfuratom and a halogen atom.

Specific examples of the divalent linking group containing a hetero atominclude —O—, —C(═O)—, —C(═O)—O—, a carbonate bond (—O—C(═O)—O—), —NH—,—NR⁰⁴—(R⁰⁴ represents a substituent such as an alkyl group or an acylgroup), —NH—C(═O)—, ═N—, —S—, —S(═O)₂—, and —S(═O)₂—O—. Further, acombination of any one of these “divalent linking groups containing ahetero atom” with a divalent hydrocarbon group can also be used. Asexamples of the divalent hydrocarbon group, the same groups as thosedescribed above for the hydrocarbon group which may have a substituentcan be given, and a linear or branched aliphatic hydrocarbon group ispreferable.

In the —NR⁰⁴— group, R⁰⁴ represents a substituent such as an alkyl groupor an acyl group. The substituent (an alkyl group, an acyl group or thelike) preferably has 1 to 10 carbon atoms, more preferably 1 to 8, andmost preferably 1 to 5.

R⁰² may or may not have an acid dissociable portion in the structurethereof.

An “acid dissociable portion” refers to a portion within the R⁰² groupwhich is dissociated from the group by action of acid generated uponexposure. When the R⁰² group has an acid dissociable portion, itpreferably has an acid dissociable portion having a tertiary carbonatom.

In the present invention, as the divalent linking group for R⁰², analkylene group, a divalent aliphatic cyclic group or a divalent linkinggroup containing a hetero atom is preferable. Among these, an alkylenegroup is particularly desirable.

When R⁰² represents an alkylene group, it preferably has 1 to 10 carbonatoms, more preferably 1 to 6, still more preferably 1 to 4, and mostpreferably 1 to 3. Specific examples of alkylene groups include theaforementioned linear alkylene groups and branched alkylene groups.

When R⁰² represents a divalent aliphatic cyclic group, as the aliphaticcyclic group, the same aliphatic cyclic groups as those described abovefor the “aliphatic hydrocarbon group containing a ring in the structurethereof” can be used.

As the aliphatic cyclic group, a group in which two or more hydrogenatoms have been removed from cyclopentane, cyclohexane, norbornane,isobornane, adamantane, tricyclodecane or tetracyclododecane isparticularly desirable.

When R⁰² represents a divalent linking group containing a hetero atom,preferable examples of the divalent linking group containing a heteroatom include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—,—NR⁰⁴—(R⁰⁴ represents a substituent such as an alkyl group or an acylgroup), —S—, —S(═O)₂—, —S(═O)₂—O—, a group represented by the formula-A-O—B—, and a group represented by the formula -[A-C(═O)—O]_(q)—B—.Herein, each of A and B independently represents a divalent hydrocarbongroup which may have a substituent, and q represents an integer of 0 to3.

In the group represented by the formula -A-O—B— or -[A-C(═O)—O]_(q)—B—,each of A and B independently represents a divalent hydrocarbon groupwhich may have a substituent.

Examples of divalent hydrocarbon groups for A and B which may have asubstituent include the same groups as those described above for the“divalent hydrocarbon group which may have a substituent” usable as R⁰².

As A, a linear aliphatic hydrocarbon group is preferable, morepreferably a linear alkylene group, still more preferably a linearalkylene group of 1 to 5 carbon atoms, and a methylene group or anethylene group is particularly desirable.

As B, a linear or branched aliphatic hydrocarbon group is preferable,and a methylene group, an ethylene group or an alkylmethylene group ismore preferable. The alkyl group within the alkylmethylene group ispreferably a linear alkyl group of 1 to 5 carbon atoms, more preferablya linear alkyl group of 1 to 3 carbon atoms, and most preferably amethyl group.

In the group represented by the formula -[A-C(═O)—O]_(q)—B—, qrepresents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1.

In general formula (a0-1), R⁰³ represents a cyclic group containing—SO₂— within the ring skeleton thereof.

The cyclic group for R⁰³ refers to a cyclic group including a ring thatcontains —SO₂— within the ring skeleton thereof, and this ring iscounted as the first ring. A cyclic group in which the only ringstructure is the ring that contains —SO₂— in the ring skeleton thereofis referred to as a monocyclic group, and a group containing other ringstructures is described as a polycyclic group regardless of thestructure of the other rings. The cyclic group for R⁰³ may be either amonocyclic group or a polycyclic group.

As R⁰³, a cyclic group containing —O—SO₂— within the ring skeletonthereof, i.e., a sultone ring is particularly desirable.

The cyclic group for R⁰³ preferably has 3 to 30 carbon atoms, morepreferably 4 to 20, still more preferably 4 to 15, and most preferably 4to 12.

Herein, the number of carbon atoms refers to the number of carbon atomsconstituting the ring skeleton, excluding the number of carbon atomswithin a substituent.

The cyclic group for R⁰³ may be either an aliphatic cyclic group or anaromatic cyclic group, and is preferably an aliphatic cyclic group.

Examples of aliphatic cyclic groups for R⁰³ include the aforementionedcyclic aliphatic hydrocarbon groups in which part of the carbon atomsconstituting the ring skeleton thereof has been substituted with —SO₂—or —O—SO₂—.

More specifically, examples of monocyclic groups include amonocycloalkane in which one hydrogen atom have been removed therefromand a —CH₂— group constituting the ring skeleton thereof has beensubstituted with —SO₂—; and a monocycloalkane in which one hydrogen atomhave been removed therefrom and a —CH₂—CH₂— group constituting the ringskeleton thereof has been substituted with —O—SO₂—. Examples ofpolycyclic groups include a polycycloalkane (a bicycloalkane, atricycloalkane, a tetracycloalkane or the like) in which one hydrogenatom have been removed therefrom and a —CH₂— group constituting the ringskeleton thereof has been substituted with —SO₂—; and a polycycloalkanein which one hydrogen atom have been removed therefrom and a —CH₂—CH₂—group constituting the ring skeleton thereof has been substituted with—O—SO₂—.

The cyclic group for R⁰³ may have a substituent. Examples of thesubstituent include an alkyl group, an alkoxy group, a halogen atom, ahalogenated alkyl group, a hydroxy group, an oxygen atom (═O), —COOR″,—OC(═O)R″, a hydroxyalkyl group and a cyano group. R″ represents ahydrogen atom or an alkyl group.

The alkyl group for the substituent is preferably an alkyl group of 1 to6 carbon atoms. Further, the alkyl group is preferably a linear alkylgroup or a branched alkyl group. Specific examples include a methylgroup, an ethyl group, a propyl group, an isopropyl group, an n-butylgroup, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group, a neopentyl group and a hexyl group. Among these, amethyl group or ethyl group is preferable, and a methyl group isparticularly desirable.

As the alkoxy group for the substituent, an alkoxy group of 1 to 6carbon atoms is preferable. Further, the alkoxy group is preferably alinear alkoxy group or a branched alkyl group. Specific examples of thealkoxy group include the aforementioned alkyl groups for the substituenthaving an oxygen atom (—O—) bonded thereto.

Examples of the halogen atom for the substituent include a fluorineatom, a chlorine atom, a bromine atom and an iodine atom, and a fluorineatom is preferable.

Examples of the halogenated alkyl group for the substituent includegroups in which part or all of the hydrogen atoms within theaforementioned alkyl groups has been substituted with the aforementionedhalogen atoms.

As examples of the halogenated lower alkyl group for the substituent,groups in which part or all of the hydrogen atoms of the aforementionedalkyl groups for the substituent have been substituted with theaforementioned halogen atoms can be given. As the halogenated alkylgroup, a fluorinated alkyl group is preferable, and a perfluoroalkylgroup is particularly desirable.

In the —COOR″ group and the —OC(═O)R″ group, R″ preferably represents ahydrogen atom or a linear, branched or cyclic alkyl group of 1 to 15carbon atoms.

When R″ represents a linear or branched alkyl group, it is preferably analkyl group of 1 to 10 carbon atoms, more preferably an alkyl group of 1to 5 carbon atoms, and most preferably a methyl group or an ethyl group.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and mostpreferably 5 to 10 carbon atoms. As examples of the cycloalkyl group,groups in which one or more hydrogen atoms have been removed from amonocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane, which may or may not be substitutedwith a fluorine atom or a fluorinated alkyl group, may be used. Specificexamples include groups in which one or more hydrogen atoms have beenremoved from a monocycloalkane such as cyclopentane and cyclohexane; andgroups in which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

The hydroxyalkyl group for the substituent preferably has 1 to 6 carbonatoms, and specific examples thereof include the aforementioned alkylgroups for the substituent in which at least one hydrogen atom has beensubstituted with a hydroxy group.

More specific examples of R⁰³ include groups represented by generalformulas (3-1) to (3-4) shown below.

In the formulas, A′ represents an oxygen atom, a sulfur atom, or analkylene group of 1 to 5 carbon atoms which may contain an oxygen atomor a sulfur atom; p represents an integer of 0 to 2; and R⁸ representsan alkyl group, an alkoxy group, a halogenated alkyl group, a hydroxylgroup, —COOR″, —OC(═O)R″, a hydroxyalkyl group or a cyano group, whereinR″ represents a hydrogen atom or an alkyl group.

In general formulas (3-1) to (3-4) above, A′ represents an oxygen atom(—O—), a sulfur atom (—S—), or an alkylene group of 1 to 5 carbon atomswhich may contain an oxygen atom or a sulfur atom.

As the alkylene group of 1 to 5 carbon atoms represented by A′, a linearor branched alkylene group is preferable, and examples thereof include amethylene group, an ethylene group, an n-propylene group and anisopropylene group.

Examples of alkylene groups that contain an oxygen atom or a sulfur atominclude the aforementioned alkylene groups in which —O— or —S— is bondedto the terminal of the alkylene group or interposed within the alkylgroup. Specific examples of such alkylene groups include —O—CH₂—,—CH₂—O—CH₂—, —S—CH₂—, —CH₂—S—CH₂—.

As A′, an alkylene group of 1 to 5 carbon atoms or —O— is preferable,more preferably an alkylene group of 1 to 5 carbon atoms, and mostpreferably a methylene group.

p represents an integer of 0 to 2, and is most preferably 0.

When p is 2, the plurality of R⁸ may be the same or different from eachother.

As the alkyl group, alkoxy group, halogenated alkyl group, halogenatedalkyl group, hydroxyl group, —COOR″, —OC(═O)R″, hydroxyalkyl group andcyano group for R⁸, the same alkyl groups, alkoxy groups, halogenatedalkyl groups, halogenated alkyl groups, hydroxyl groups, —COOR″,—OC(═O)R″, hydroxyalkyl groups and cyano groups as those described aboveas the substituent for the cyclic group represented by R⁰³ can be used.

Specific examples of the cyclic groups represented by general formulas(3-1) to (3-4) are shown below. In the formulas shown below, “Ac”represents an acetyl group.

Among the examples shown above, as R⁰³, a cyclic group represented bygeneral formula (3-1), (3-3) or (3-4) above is preferable, and a cyclicgroup represented by general formula (3-1) above is particularlydesirable.

More specifically, as R⁰³, it is preferable to use at least one cyclicgroup selected from the group consisting of cyclic groups represented bychemical formulas (3-1-1), (3-1-18), (3-3-1) and (3-4-1) above, and acyclic group represented by chemical formula (3-1-1) above isparticularly desirable.

In the present invention, as the structural unit (a0), a structural unitrepresented by general formula (a0-1-11) shown below is particularlydesirable.

In the formula, R is the same as defined above; R⁰² represents a linearor branched alkylene group or -A-C(═O)—O—B— (wherein A and B are thesame as defined above); and A′ is the same as defined above.

The linear or branched alkylene group for R⁰² preferably has 1 to 10carbon atoms, more preferably 1 to 8, still more preferably 1 to 5,still more preferably 1 to 3, and most preferably 1 or 2.

In the -A-C(═O)—O—B— group, each of A and B preferably represents alinear or branched alkylene group, more preferably an alkylene group of1 to 5 carbon atoms, and most preferably a methylene group or anethylene group. Specific examples thereof include—(CH₂)₂—C(═O)—O—(CH₂)₂—, and —(CH₂)₂—O—C(═O)—(CH₂)₂—.

A′ is preferably a methylene group, an oxygen atom (—O—) or a sulfuratom (—S—).

As the structural unit (a0), one type of structural unit may be usedalone, or two or more types of structural units may be used incombination.

In terms of achieving excellent lithography properties such as exposuremargin (EL margin), line width roughness (LWR) and the like in theformation of a resist pattern using a positive resist compositioncontaining the component (A1), the amount of the structural unit (a0)within the component (A1), based on the combined total of all structuralunits constituting the component (A1) is preferably 1 to 60 mol %, morepreferably 5 to 55 mol %, still more preferably 10 to 50 mol %, and mostpreferably 15 to 45 mol %.

(Structural Unit (a1))

The structural unit (a1) is a structural unit derived from an acrylateester containing an acid dissociable, dissolution inhibiting group anddoes not fall under the category of the aforementioned structural unit(a0).

As the acid dissociable, dissolution inhibiting group in the structuralunit (a1), any of the groups that have been proposed as aciddissociable, dissolution inhibiting groups for the base resins ofchemically amplified resists can be used, provided the group has analkali dissolution-inhibiting effect that renders the entire component(A1) insoluble in an alkali developing solution prior to dissociation,and then following dissociation by action of acid, increases thesolubility of the entire component (A1) in the alkali developingsolution. Generally, groups that form either a cyclic or chain-liketertiary alkyl ester with the carboxyl group of the (meth)acrylic acid,and acetal-type acid dissociable, dissolution inhibiting groups such asalkoxyalkyl groups are widely known.

Here, a tertiary alkyl ester describes a structure in which an ester isformed by substituting the hydrogen atom of a carboxyl group with achain-like or cyclic tertiary alkyl group, and a tertiary carbon atomwithin the chain-like or cyclic tertiary alkyl group is bonded to theoxygen atom at the terminal of the carbonyloxy group (—C(═O)—O—). Inthis tertiary alkyl ester, the action of acid causes cleavage of thebond between the oxygen atom and the tertiary carbon atom.

The chain-like or cyclic alkyl group may have a substituent.

Hereafter, for the sake of simplicity, groups that exhibit aciddissociability as a result of the formation of a tertiary alkyl esterwith a carboxyl group are referred to as “tertiary alkyl ester-type aciddissociable, dissolution inhibiting groups”.

Examples of tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups include aliphatic branched, acid dissociable,dissolution inhibiting groups and aliphatic cyclic group-containing aciddissociable, dissolution inhibiting groups.

The term “aliphatic branched” refers to a branched structure having noaromaticity. The “aliphatic branched, acid dissociable, dissolutioninhibiting group” is not limited to be constituted of only carbon atomsand hydrogen atoms (not limited to hydrocarbon groups), but ispreferably a hydrocarbon group.

Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated.

As an example of the aliphatic branched, acid dissociable, dissolutioninhibiting group, for example, a group represented by the formula—C(R⁷¹)(R⁷²)(R⁷³) can be given (in the formula, each of R⁷¹ to R⁷³independently represents a linear alkyl group of 1 to 5 carbon atoms).The group represented by the formula —C(R⁷¹)(R⁷²)(R⁷³) preferably has 4to 8 carbon atoms, and specific examples include a tert-butyl group, a2-methyl-2-butyl group, a 2-methyl-2-pentyl group and a3-methyl-3-pentyl group. Among these, a tert-butyl group is particularlydesirable.

The term “aliphatic cyclic group” refers to a monocyclic group orpolycyclic group that has no aromaticity.

The “aliphatic cyclic group” within the structural unit (a1) may or maynot have a substituent. Examples of the substituent include an alkylgroup of 1 to 5 carbon atoms, an alkoxy group of 1 to 5 carbon atoms, afluorine atom, a fluorinated alkyl group of 1 to 5 carbon atoms, and anoxygen atom (═O).

The basic ring of the “aliphatic cyclic group” exclusive of substituentsis not limited to be constituted from only carbon and hydrogen (notlimited to hydrocarbon groups), but is preferably a hydrocarbon group.

Further, the “hydrocarbon group” may be either saturated or unsaturated,but is preferably saturated. Furthermore, the “aliphatic cyclic group”is preferably a polycyclic group.

As such aliphatic cyclic groups, groups in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane which may or maynot be substituted with a lower alkyl group, a fluorine atom or afluorinated alkyl group, may be used. Specific examples include groupsin which one or more hydrogen atoms have been removed from amonocycloalkane such as cyclopentane or cyclohexane; and groups in whichone or more hydrogen atoms have been removed from a polycycloalkane suchas adamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Further, these groups in which one or more hydrogenatoms have been removed from a monocycloalkane and groups in which oneor more hydrogen atoms have been removed from a polycycloalkane may havepart of the carbon atoms constituting the ring replaced with an etherealoxygen atom (—O—).

Examples of aliphatic cyclic group-containing acid dissociable,dissolution inhibiting groups include

(i) a group which has a tertiary carbon atom on the ring structure of amonovalent aliphatic cyclic group; and

(ii) a group which has a branched alkylene group containing a tertiarycarbon atom, and a monovalent aliphatic cyclic group to which thetertiary carbon atom is bonded.

Specific examples of (i) a group which has a tertiary carbon atom on thering structure of a monovalent aliphatic cyclic group include groupsrepresented by general formulas (1-1) to (1-9) shown below.

Specific examples of (ii) a group which has a branched alkylene groupcontaining a tertiary carbon atom, and a monovalent aliphatic cyclicgroup to which the tertiary carbon atom is bonded include groupsrepresented by general formulas (2-1) to (2-6) shown below.

In the formulas above, R¹⁴ represents an alkyl group; and g representsan integer of 0 to 8.

In the formulas above, each of R¹⁵ and R¹⁶ independently represents analkyl group.

As the alkyl group for R¹⁴, a linear or branched alkyl group ispreferable.

The linear alkyl group preferably has 1 to 5 carbon atoms, morepreferably 1 to 4, and still more preferably 1 or 2. Specific examplesinclude a methyl group, an ethyl group, an n-propyl group, an n-butylgroup and an n-pentyl group. Among these, a methyl group, an ethyl groupor an n-butyl group is preferable, and a methyl group or an ethyl groupis more preferable.

The branched alkyl group preferably has 3 to 10 carbon atoms, and morepreferably 3 to 5. Specific examples of such branched alkyl groupsinclude an isopropyl group, an isobutyl group, a tert-butyl group, anisopentyl group and a neopentyl group, and an isopropyl group isparticularly desirable.

g is preferably an integer of 0 to 3, more preferably 1 to 3, and stillmore preferably 1 or 2.

As the alkyl group for R¹⁵ and R¹⁶, the same alkyl groups as those forR¹⁴ can be used.

In formulas (1-1) to (1-9) and (2-1) to (2-6), part of the carbon atomsconstituting the ring may be replaced with an ethereal oxygen atom(—O—).

Further, in formulas (1-1) to (1-9) and (2-1) to (2-6), one or more ofthe hydrogen atoms bonded to the carbon atoms constituting the ring maybe substituted with a substituent. Examples of the substituent includean alkyl group of 1 to 5 carbon atoms, a fluorine atom and a fluorinatedalkyl group.

An “acetal-type acid dissociable, dissolution inhibiting group”generally substitutes a hydrogen atom at the terminal of analkali-soluble group such as a carboxy group or hydroxyl group, so as tobe bonded with an oxygen atom. When acid is generated upon exposure, thegenerated acid acts to break the bond between the acetal-type aciddissociable, dissolution inhibiting group and the oxygen atom to whichthe acetal-type, acid dissociable, dissolution inhibiting group isbonded.

Examples of acetal-type acid dissociable, dissolution inhibiting groupsinclude groups represented by general formula (p1) shown below.

In the formula, R¹′ and R²′ each independently represent a hydrogen atomor an alkyl group of 1 to 5 carbon atoms; n represents an integer of 0to 3; and Y represents an alkyl group of 1 to 5 carbon atoms or analiphatic cyclic group.

In general formula (p1) above, n is preferably an integer of 0 to 2,more preferably 0 or 1, and most preferably 0.

As the alkyl group of 1 to 5 carbon atoms for R¹′ and R²′, the samealkyl groups of 1 to 5 carbon atoms as those described above for R canbe used, although a methyl group or ethyl group is preferable, and amethyl group is particularly desirable.

In the present invention, it is preferable that at least one of R¹′ andR²′ be a hydrogen atom. That is, it is preferable that the aciddissociable, dissolution inhibiting group (p1) is a group represented bygeneral formula (p1-1) shown below.

In the formula, R¹′, n and Y are the same as defined above.

As the alkyl group of 1 to 5 carbon atoms for Y, the same alkyl groupsof 1 to 5 carbon atoms as those for R above can be used.

As the aliphatic cyclic group for Y, any of the aliphaticmonocyclic/polycyclic groups which have been proposed for conventionalArF resists and the like can be appropriately selected for use. Forexample, the same groups described above in connection with the“aliphatic cyclic group” can be used.

Further, as the acetal-type, acid dissociable, dissolution inhibitinggroup, groups represented by general formula (p2) shown below can alsobe used.

In the formula, R¹⁷ and R¹⁸ each independently represent a linear orbranched alkyl group or a hydrogen atom; and R¹⁹ represents a linear,branched or cyclic alkyl group; or R¹⁷ and R¹⁹ each independentlyrepresents a linear or branched alkylene group, and the terminal of R¹⁷is bonded to the terminal of R¹⁹ to form a ring.

The alkyl group for R¹⁷ and R¹⁸ preferably has 1 to 15 carbon atoms, andmay be either linear or branched. As the alkyl group, an ethyl group ora methyl group is preferable, and a methyl group is most preferable. Itis particularly desirable that either one of R¹⁷ and R¹⁸ be a hydrogenatom, and the other be a methyl group.

R¹⁹ represents a linear, branched or cyclic alkyl group which preferablyhas 1 to 15 carbon atoms, and may be any of linear, branched or cyclic.

When R¹⁹ represents a linear or branched alkyl group, it is preferablyan alkyl group of 1 to 5 carbon atoms, more preferably an ethyl group ora methyl group, and an ethyl group is particularly desirable.

When R¹⁹ represents a cycloalkyl group, it preferably has 4 to 15 carbonatoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10carbon atoms. As examples of the cycloalkyl group, groups in which oneor more hydrogen atoms have been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane, which may or may not be substituted with a fluorineatom or a fluorinated alkyl group, may be used. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane such as cyclopentane and cyclohexane; and groupsin which one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane. Among these, a group in which oneor more hydrogen atoms have been removed from adamantane is preferable.

In general formula (p2) above, R¹⁷ and R¹⁹ may each independentlyrepresent a linear or branched alkylene group (preferably an alkylenegroup of 1 to 5 carbon atoms), and the terminal of R¹⁹ may be bonded tothe terminal of R¹⁷.

In such a case, a cyclic group is formed by R¹⁷, R¹⁹, the oxygen atomhaving R¹⁹ bonded thereto, and the carbon atom having the oxygen atomand R¹⁷ bonded thereto.

Such a cyclic group is preferably a 4- to 7-membered ring, and morepreferably a 4- to 6-membered ring. Specific examples of the cyclicgroup include tetrahydropyranyl group and tetrahydrofuranyl group.

Specific examples of acetal-type acid dissociable, dissolutioninhibiting groups include groups represented by formulas (p3-1) to(p3-12) shown below.

In the formulas above, R¹³ represents a hydrogen atom or a methyl group;and g is the same as defined above.

Specific examples of the structural unit (a1) include a structural unitrepresented by general formula (a1-0-1) shown below and a structuralunit represented by general formula (a1-0-2) shown below.

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; X¹represents an acid dissociable, dissolution inhibiting group; Y²represents a divalent linking group; and X² represents an aciddissociable, dissolution inhibiting group.

In general formula (a1-0-1), R is the same as defined for R in generalformula (a0-1).

X¹ is not particularly limited as long as it is an acid dissociable,dissolution inhibiting group. Examples thereof include theaforementioned tertiary alkyl ester-type acid dissociable, dissolutioninhibiting groups and acetal-type acid dissociable, dissolutioninhibiting groups, and tertiary alkyl ester-type acid dissociable,dissolution inhibiting groups are preferable.

In general formula (a1-0-2), R is the same as defined above.

X² is the same as defined for X¹ in general formula (a1-0-1).

As examples of the divalent linking group for Y², the same groups asthose described above for R⁰² in formula (a0-1) can be given.

As Y⁰², the aforementioned alkylene group, a divalent aliphatic cyclicgroup or a divalent linking group containing a hetero atom described inthe explanation of R² is preferable. Among these, a divalent linkinggroup containing a hetero atom is preferable, and a linear groupcontaining an oxygen atom as a heteratom, e.g., a group containing anester bond is particularly desirable.

More specifically, a group represented by the aforementioned formula-A-O—B— or -A-C(═O)—O—B— is preferable, and a group represented by theformula —(CH₂)_(x)—C(═O)—O—(CH₂)_(y)— is particularly desirable.

x represents an integer of 1 to 5, preferably 1 or 2, and mostpreferably 1.

y represents an integer of 1 to 5, preferably 1 or 2, and mostpreferably 1.

Specific examples of the structural unit (a1) include structural unitsrepresented by general formulas (a1-1) to (a1-4) shown below.

In the formulas, X′ represents a tertiary alkyl ester-type aciddissociable, dissolution inhibiting group; Y represents an alkyl groupof 1 to 5 carbon atoms or an aliphatic cyclic group; n represents aninteger of 0 to 3; Y² represents a divalent linking group; R is the sameas defined above; and each of R¹′ and R²′ independently represents ahydrogen atom or an alkyl group of 1 to 5 carbon atoms.

Examples of the tertiary alkyl ester-type acid dissociable, dissolutioninhibiting group for X′ include the same tertiary alkyl ester-type aciddissociable, dissolution inhibiting groups as those described above forX¹.

As R¹′, R²′, n and Y are respectively the same as defined for R¹′, R²′,n and Y in general formula (p1) described above in connection with the“acetal-type acid dissociable, dissolution inhibiting group”.

As examples of Y², the same groups as those described above for Y² ingeneral formula (a1-0-2) can be given.

Specific examples of structural units represented by general formula(a1-1) to (a1-4) are shown below.

In the formulas shown below, R^(α) represents a hydrogen atom, a methylgroup or a trifluoromethyl group.

As the structural unit (a1), one type of structural unit may be usedalone, or two or more types of structural units may be used incombination.

In the present invention, as the structural unit (a1), a structural unitrepresented by general formula (a1-1-01) shown below which includes theaforementioned formulas (a1-1-1), (a1-1-2) and (a1-1-7) to (a1-1-15)described above as examples of structural units represented by generalformula (a1-1) is particularly desirable in terms of achieving excellentlithography properties (e.g., EL margin, LWR, resolution and the like)and an excellent resist pattern shape.

As a structural unit represented by general formula (a1-1-01) shownbelow, a structural unit represented by general formula (a1-1-101) shownbelow which includes the aforementioned formulas (a1-1-1) and (a1-1-2)is particularly desirable.

In the formulas, R is the same as defined above; each of R⁵⁵ and R¹¹independently represents a linear alkyl group of 1 to 5 carbon atoms;and R⁵⁴ represents a group which forms an aliphatic polycyclic grouptogether with the carbon atom bonded to the R⁵⁴ group.

In general formula (a1-1-01), as the aliphatic polycyclic group formedby R⁵⁴ and the carbon atom to which R⁵⁴ is bonded, the same aliphaticcyclic groups as those described above for the aforementioned tertiaryalkyl ester-type acid dissociable, dissolution inhibiting group andwhich are polycyclic can be used.

Further, it is preferable that the component (A1) include, as thestructural unit (a1), at least one member selected from the groupconsisting of a structural unit represented by general formula (a1-0-11)shown below, a structural unit represented by general formula (a1-0-12)shown below, and a structural unit represented by general formula(a1-0-2) shown below.

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; R⁵¹represents an alkyl group; R⁵² represents a group which forms analiphatic monocyclic group with the carbon atom to which R⁵² is bonded;R⁵³ represents a branched alkyl group; R⁵⁴ is the same as defined forR⁵⁴ in general formula (a1-1-01); Y² represents a divalent linkinggroup; and X² represents an acid dissociable, dissolution inhibitinggroup.

In the formulas, R, Y² and X² are the same as defined above.

In general formula (a1-0-11), as the alkyl group for R⁵¹, the same alkylgroups as those described above for R¹⁴ in formulas (1-1) to (1-9) canbe used, preferably a methyl group or an ethyl group, and mostpreferably an ethyl group.

As the aliphatic monocyclic group formed by R⁵² and the carbon atoms towhich R⁵² is bonded, the same aliphatic cyclic groups as those describedabove for the aforementioned tertiary alkyl ester-type acid dissociable,dissolution inhibiting group and which are monocyclic can be used.Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane. The monocycloalkane ispreferably a 3- to 11-membered ring, more preferably a 3- to 8-memberedring, still more preferably a 4- to 6-membered ring, and most preferablya 5- or 6-membered ring.

The monocycloalkane may or may not have part of the carbon atomsconstituting the ring replaced with an ethereal oxygen atom (—O—).

Further, the monocycloalkane may have a substituent such as an alkylgroup of 1 to 5 carbon atoms, a fluorine atom or a fluorinated alkylgroup.

As an examples of R⁵² constituting such an aliphatic cyclic group, analkylene group which may have an ethereal oxygen atom (—O—) interposedbetween the carbon atoms can be given.

Specific examples of structural units represented by general formula(a1-0-11) include structural units represented by the aforementionedformulas (a1-1-16) to (a1-1-23). Among these, a structural unitrepresented by general formula (a1-1-02) shown below which includes thestructural units represented by the aforementioned formulas (a0-1-16),(a1-1-17), (a1-1-20) to (a1-1-23), (a1-1-32) and (a1-1-33) ispreferable. Further, a structural unit represented by general formula(a1-1-02′) shown below is also preferable.

In the formulas shown below, h is preferably 1 or 2, and most preferably2.

In the formulas, R and R⁵¹ are the same as defined above; and hrepresents an integer of 1 to 6.

In general formula (a1-0-12), as the branched alkyl group for R⁵³, thesame alkyl groups as those described above for R¹⁴ in formulas (1-1) to(1-9) which are branched can be used, and an isopropyl group isparticularly desirable.

R⁵⁴ is the same as defined for R⁵⁴ in formula (a1-1-01).

Specific examples of structural units represented by general formula(a1-0-12) include structural units represented by the aforementionedformulas (a1-1-26) to (a1-1-31).

Examples of structural units represented by general formula (a1-0-2)include structural units represented by the aforementioned formulas(a1-3) and (a1-4), and a structural unit represented by formula (a1-3)is preferable.

As a structural unit represented by general formula (a1-0-2), those inwhich Y² is a group represented by the aforementioned formula -A-O—B— or-A-C(═O)—O—B— is particularly desirable.

Preferable examples of such structural units include a structural unitrepresented by general formula (a1-3-01) shown below, a structural unitrepresented by general formula (a1-3-02) shown below, and a structuralunit represented by general formula (a1-3-03) shown below.

In the formula, R and R¹⁴ are the same as defined above; R¹² representsa hydrogen atom or a methyl group; and v represents an integer of 1 to10.

In the formula, R and R¹⁴ are the same as defined above; R¹² representsa hydrogen atom or a methyl group; v represents an integer of 1 to 10;and n′ represents an integer of 0 to 3.

In the formula, R is as defined above; each of Y²′ and Y²″ independentlyrepresents a divalent linking group; X′ represents an acid dissociable,dissolution inhibiting group; and n represents an integer of 1 to 3.

In general formulas (a1-3-01) and (a1-3-02), R¹² is preferably ahydrogen atom. v is preferably an integer of 1 to 8, more preferably 1to 5, and most preferably 1 or 2.

n′ is preferably 1 or 2, and most preferably 2.

Specific examples of structural units represented by general formula(a1-3-01) include structural units represented by the aforementionedformulas (a1-3-25) and (a1-3-26).

Specific examples of structural units represented by general formula(a1-3-02) include structural units represented by the aforementionedformulas (a1-3-27) and (a1-3-28).

In general formula (a1-3-03), as the divalent linking group for Y²′ andY²″, the same groups as those described above for Y² in general formula(a1-3) can be used.

As Y²′, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As Y²″, a divalent hydrocarbon group which may have a substituent ispreferable, a linear aliphatic hydrocarbon group is more preferable, anda linear alkylene group is still more preferable. Among linear alkylenegroups, a linear alkylene group of 1 to 5 carbon atoms is preferable,and a methylene group or an ethylene group is particularly desirable.

As the acid dissociable, dissolution inhibiting group for X′, the samegroups as those described above can be used. X′ is preferably a tertiaryalkyl ester-type acid dissociable, dissolution inhibiting group, morepreferably the aforementioned group (i) which has a tertiary carbon atomon the ring structure of a monovalent aliphatic cyclic group. Among theaforementioned groups (i), a group represented by general formula (1-1)above is preferable.

n represents an integer of 0 to 3, preferably an integer of 0 to 2, morepreferably 0 or 1, and most preferably 1.

As the structural unit represented by general formula (a1-3-03), astructural unit represented by general formula (a1-3-03-1) or(a1-3-03-2) shown below is preferable. Among these, a structural unitrepresented by general formula (a1-3-03-1) is preferable, and astructural unit represented by the aforementioned formula (a1-3-29) or(a1-3-30) is particularly desirable.

In the formulas, R and R¹⁴ are the same as defined above; v representsan integer of 1 to 10; w represents an integer of 1 to 10; and trepresents an integer of 0 to 3.

v is preferably an integer of 1 to 5, and most preferably 1 or 2.

w is preferably an integer of 1 to 5, and most preferably 1 or 2.

t is preferably an integer of 1 to 3, and most preferably 1 or 2.

In the component (A1), the amount of the structural unit (a1) based onthe combined total of all structural units constituting the component(A1) is preferably 10 to 80 mol %, more preferably 20 to 70 mol %, andstill more preferably 25 to 65 mol %. When the amount of the structuralunit (a1) is at least as large as the lower limit of the above-mentionedrange, a pattern can be easily formed using a resist compositionprepared from the component (A1). On the other hand, when the amount ofthe structural unit (a1) is no more than the upper limit of theabove-mentioned range, a good balance can be achieved with the otherstructural units.

(Structural Unit (a3))

The structural unit (a3) is a structural unit derived from an acrylateester containing a polar group-containing aliphatic hydrocarbon group.

When the component (A1) includes the structural unit (a3), thehydrophilicity of the component (A) is improved, and hence, thecompatibility of the component (A) with the developing solution isimproved. As a result, the alkali solubility of the exposed portionsimproves, which contributes to favorable improvements in the resolution.

Examples of the polar group include a hydroxyl group, cyano group,carboxyl group, or hydroxyalkyl group in which some of the hydrogenatoms of the alkyl group have been substituted with fluorine atoms,although a hydroxyl group is particularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branchedhydrocarbon groups (preferably alkylene groups) of 1 to 10 carbon atoms,and cyclic aliphatic hydrocarbon groups (cyclic groups). These cyclicgroups can be selected appropriately from the multitude of groups thathave been proposed for the resins of resist compositions designed foruse with ArF excimer lasers. The cyclic group is preferably a polycyclicgroup, more preferably a polycyclic group of 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylateester that include an aliphatic polycyclic group that contains ahydroxyl group, cyano group, carboxyl group or a hydroxyalkyl group inwhich part of the hydrogen atoms of the alkyl group have beensubstituted with fluorine atoms are particularly desirable. Examples ofthe polycyclic group include groups in which two or more hydrogen atomshave been removed from a bicycloalkane, tricycloalkane, tetracycloalkaneor the like. Specific examples include groups in which two or morehydrogen atoms have been removed from a polycycloalkane such asadamantane, norbornane, isobornane, tricyclodecane ortetracyclododecane. Of these polycyclic groups, groups in which two ormore hydrogen atoms have been removed from adamantane, norbornane ortetracyclododecane are preferred industrially.

When the aliphatic hydrocarbon group within the polar group-containingaliphatic hydrocarbon group is a linear or branched hydrocarbon group of1 to 10 carbon atoms, the structural unit (a3) is preferably astructural unit derived from a hydroxyethyl ester of acrylic acid. Onthe other hand, when the hydrocarbon group is a polycyclic group,structural units represented by formulas (a3-1), (a3-2) and (a3-3) shownbelow are preferable.

In the formulas, R is the same as defined above; j is an integer of 1 to3; k is an integer of 1 to 3; t′ is an integer of 1 to 3; 1 is aninteger of 1 to 5; and s is an integer of 1 to 3.

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When jis 2, it is preferable that the hydroxyl groups be bonded to the 3rd and5th positions of the adamantyl group. When j is 1, it is preferable thatthe hydroxyl group be bonded to the 3rd position of the adamantyl group.j is preferably 1, and it is particularly desirable that the hydroxylgroup be bonded to the 3rd position of the adamantyl group.

In formula (a3-2), k is preferably 1. The cyano group is preferablybonded to the 5th or 6th position of the norbornyl group.

In formula (a3-3), t′ is preferably 1. l is preferably 1. s ispreferably 1. Further, it is preferable that a 2-norbornyl group or3-norbornyl group be bonded to the terminal of the carboxy group of theacrylic acid. The fluorinated alkyl alcohol is preferably bonded to the5th or 6th position of the norbornyl group.

As the structural unit (a3), one type of structural unit may be used, ortwo or more types may be used in combination.

The amount of the structural unit (a3) within the component (A1) basedon the combined total of all structural units constituting the component(A1) is preferably 5 to 50 mol %, more preferably 5 to 40 mol %, andstill more preferably 5 to 25 mol %. When the amount of the structuralunit (a3) is at least as large as the lower limit of the above-mentionedrange, the effect of using the structural unit (a3) can besatisfactorily achieved. On the other hand, when the amount of thestructural unit (a3) is no more than the upper limit of theabove-mentioned range, a good balance can be achieved with the otherstructural units.

(Other Structural Units)

The component (A1) may also have a structural unit other than theabove-mentioned structural units (a0), (a1) and (a3), as long as theeffects of the present invention are not impaired.

As such a structural unit, any other structural unit which cannot beclassified as one of the above structural units (a0), (a1) and (a3) canbe used without any particular limitations, and any of the multitude ofconventional structural units used within resist resins for ArF excimerlasers or KrF excimer lasers (and particularly for ArF excimer lasers)can be used.

Examples of other structural units include a structural unit (a2) is astructural unit derived from an acrylate ester containing alactone-containing cyclic group, a structural unit (a4) derived from anacrylate ester containing a non-acid-dissociable aliphatic polycyclicgroup, and a structural unit (a5) represented by general formula (a5-1)which will be described later.

—Structural Unit (a2)

The structural unit (a2) is a structural unit derived from an acrylateester containing a lactone-containing cyclic group.

The term “lactone-containing cyclic group” refers to a cyclic groupincluding one ring containing a —O—C(O)— structure (lactone ring). Theterm “lactone ring” refers to a single ring containing a —O—C(O)—structure, and this ring is counted as the first ring. Alactone-containing cyclic group in which the only ring structure is thelactone ring is referred to as a monocyclic group, and groups containingother ring structures are described as polycyclic groups regardless ofthe structure of the other rings.

When the component (A1) is used for forming a resist film, thelactone-containing cyclic group of the structural unit (a2) is effectivein improving the adhesion between the resist film and the substrate, andincreasing the compatibility with the developing solution containingwater.

As the structural unit (a2), there is no particular limitation, and anarbitrary structural unit may be used.

Specific examples of lactone-containing monocyclic groups include agroup in which one hydrogen atom has been removed from a 4- to6-membered lactone ring, such as a group in which one hydrogen atom hasbeen removed from β-propiolatone, a group in which one hydrogen atom hasbeen removed from γ-butyrolactone, and a group in which one hydrogenatom has been removed from δ-valerolactone. Further, specific examplesof lactone-containing polycyclic groups include groups in which onehydrogen atom has been removed from a lactone ring-containingbicycloalkane, tricycloalkane or tetracycloalkane.

More specifically, examples of the structural unit (a2) includestructural units represented by general formulas (a2-1) to (a2-5) shownbelow.

In the formulas, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; eachR′ independently represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms, an alkoxy group of 1 to 5 carbon atoms or —COOR″, whereinR″ represents a hydrogen atom or an alkyl group; R²⁹ represents a singlebond or a divalent linking group; s″ represents an integer of 0 to 2; A″represents an oxygen atom, a sulfur atom or an alkylene group of 1 to 5carbon atoms which may contain an oxygen atom or a sulfur atom; and mrepresents 0 or 1.

In general formulas (a2-1) to (a2-5), R is the same as defined for R inthe structural unit (a1).

As examples of R′, the same groups as those described above for R⁸ ingeneral formula (3-1) can be given. In terms of industrial availability,R′ is preferably a hydrogen atom.

As examples of A″, the same groups as those described above for A′ ingeneral formula (3-1) can be given.

R²⁹ represents a single bond or a divalent linking group. Examples ofdivalent linking groups include the same divalent linking groups asthose described above for R⁰² in general formula (a0-1). Among these, analkylene group, an ester bond (—C(═O)—O—) or a combination thereof ispreferable. The alkylene group as a divalent linking group for R²⁹ ispreferably a linear or branched alkylene group. Specific examplesinclude the same linear alkylene groups and branched alkylene groups asthose described above for R⁰² _(.)

s″ is preferably 1 or 2.

Specific examples of structural units represented by general formulas(a2-1) to (a2-5) are shown below. In the formulas shown below, R^(α)represents a hydrogen atom, a methyl group or a trifluoromethyl group.

In the component (A1), as the structural unit (a2), one type ofstructural unit may be used, or two or more types may be used incombination.

In the present invention, it is particularly desirable that thecomponent (A1) contain, as a structural unit (a2), at least onestructural unit selected from the group consisting of a structural unitrepresented by general formula (a2-1) and a structural unit representedby general formula (a2-2).

In terms of improving the adhesion between a substrate and a resist filmformed using a positive resist composition containing the component (A1)and increasing the compatibility with a developing solution, the amountof the structural unit (a2) within the component (A1), based on thecombined total of all structural units constituting the component (A1)is preferably 1 to 50 mol %, more preferably 5 to 50 mol %, and stillmore preferably 10 to 45 mol %. When the amount of the structural unit(a2) is at least as large as the lower limit of the above-mentionedrange, the effect of using the structural unit (a2) can besatisfactorily achieved. On the other hand, when the amount of thestructural unit (a2) is no more than the upper limit of theabove-mentioned range, a good balance can be achieved with the otherstructural units. By ensuring the above-mentioned range, variouslithography properties can be further improved.

—Structural Unit (a4)

The structural unit (a4) is a structural unit derived from an acrylateester containing a non-acid dissociable, aliphatic polycyclic group.

Examples of this polycyclic group include the same groups as thosedescribed above in relation to the aforementioned structural unit (a1),and any of the multitude of conventional polycyclic groups used withinthe resin component of resist compositions for ArF excimer lasers or KrFexcimer lasers (and particularly for ArF excimer lasers) can be used.

In consideration of industrial availability and the like, at least onepolycyclic group selected from amongst a tricyclodecanyl group,adamantyl group, tetracyclododecanyl group, isobornyl group, andnorbornyl group is particularly desirable. These polycyclic groups maybe substituted with a linear or branched alkyl group of 1 to 5 carbonatoms.

Specific examples of the structural unit (a4) include units withstructures represented by general formulas (a-4-1) to (a-4-5) shownbelow.

In the formulas, R is the same as defined above.

When the structural unit (a4) is included in the component (A1), theamount of the structural unit (a4) based on the combined total of allthe structural units that constitute the component (A1) is preferablywithin the range from 1 to 30 mol %, and more preferably from 10 to 20mol %.

—Structural Unit (a5)

The structural unit (a5) is a structural unit represented by generalformula (a5-1) shown below.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; andR⁸⁸ represents a divalent aliphatic hydrocarbon group of 2 to 12 carbonatoms which may have an oxygen atom.

In general formula (a5-1), R is the same as defined above for R in thestructural unit (a1).

In general formula (a5-1), R⁸⁸ represents a divalent aliphatichydrocarbon group of 2 to 12 carbon atoms which may have an oxygen atom.

The divalent aliphatic hydrocarbon group of 2 to 12 carbon atomsrepresented by R⁸⁸ may or may not contain an oxygen atom.

The divalent aliphatic hydrocarbon group “has an oxygen atom” means thatpart or all of the hydrogen atoms within the divalent aliphatichydrocarbon group and/or part of the carbon atoms within the divalentaliphatic hydrocarbon group is substituted with an oxygen atom.

A “divalent aliphatic hydrocarbon group” refers to a divalenthydrocarbon group that has no aromaticity.

The divalent aliphatic hydrocarbon group may be either saturated orunsaturated. In general, the divalent aliphatic hydrocarbon group ispreferably saturated.

Further, the divalent aliphatic hydrocarbon group may be a divalentaliphatic hydrocarbon group having a substituent. The expression “has asubstituent” means that part or all of the hydrogen atoms within thedivalent aliphatic hydrocarbon group is substituted with groups or atomsother than hydrogen atom.

As specific examples of the divalent aliphatic hydrocarbon group, alinear or branched, divalent aliphatic hydrocarbon group, and a divalentaliphatic hydrocarbon group containing a ring in the structure thereofcan be given.

The linear or branched, divalent aliphatic hydrocarbon group preferablyhas 2 to 10 carbon atoms, more preferably 2 to 8, and most preferably 3to 6.

As a linear, divalent aliphatic hydrocarbon group, a linear alkylenegroup is preferable, and specific examples include a methylene group, anethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], atetramethylene group [—(CH₂)₄—], a pentamethylene group [—(CH₂)₅—] and ahexamethylene group [—(CH₂)₆—].

As the branched, divalent aliphatic hydrocarbon group, branched alkylenegroups are preferred, and specific examples include variousalkylalkylene groups, including alkylmethylene groups such as —CH(CH₃)—,—CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and—C(CH₂CH₃)₂—; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—;alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—;and alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The linear or branched, divalent aliphatic hydrocarbon group(chain-like, divalent aliphatic hydrocarbon group) may or may not have asubstituent. Examples of the substituent include a fluorine atom, afluorinated alkyl group of 1 to 5 carbon atoms and an oxygen atom (═O).Among these, an oxygen atom (═O) is preferable.

As examples of the divalent hydrocarbon group containing a ring in thestructure thereof, a cyclic aliphatic hydrocarbon group (a group inwhich two hydrogen atoms have been removed from an aliphatic hydrocarbonring), and a group in which the cyclic aliphatic hydrocarbon group isbonded to the terminal of the aforementioned chain-like, divalentaliphatic hydrocarbon group or interposed within the aforementionedchain-like, divalent aliphatic hydrocarbon group, can be given.

The cyclic aliphatic hydrocarbon group preferably has 3 to 12 carbonatoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic groupor a monocyclic group. As the monocyclic group, a group in which twohydrogen atoms have been removed from a monocycloalkane of 3 to 6 carbonatoms is preferable. Examples of the monocycloalkane includecyclopentane and cyclohexane. As the polycyclic group, a group in whichtwo hydrogen atoms have been removed from a polycycloalkane of 7 to 12carbon atoms is preferable. Examples of the polycycloalkane includeadamantane, norbornane, isobornane, tricyclodecane andtetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include an alkyl group of 1 to5 carbon atoms, a fluorine atom, a fluorinated alkyl group of 1 to 5carbon atoms, and an oxygen atom (═O).

Examples of the divalent aliphatic hydrocarbon group containing anoxygen atom include groups in which —O—, —C(═O)—, —O—C(═O)—, —C(═O)—O—,a carbonate bond (—O—C(═O)—O—), —S(═O)₂—, —S(═O)₂—O— or —NH—C(═O)— isbonded to a terminal of the aforementioned chain-like, aliphatichydrocarbon group, interposed within the aforementioned chain-like,aliphatic hydrocarbon group or substituting a carbon atom thatconstitutes part of the ring skeleton of the aforementioned cyclicaliphatic hydrocarbon group.

In the present invention, as the divalent aliphatic hydrocarbon group of2 to 12 carbon atoms represented by R⁸⁸ which may contain an oxygenatom, an alkylene group or a divalent aliphatic hydrocarbon groupcontaining an oxygen atom is preferable. Among these, a divalentaliphatic hydrocarbon group containing an oxygen atom is particularlydesirable.

When R⁸⁸ represents an alkylene group, the alkylene group preferably has2 to 10 carbon atoms, and most preferably 2 to 6 carbon atoms. Specificexamples of alkylene groups include the aforementioned linear alkylenegroups and branched alkylene groups.

Preferable examples of the divalent aliphatic hydrocarbon grouprepresented by R⁸⁸ that contains an oxygen atom include a grouprepresented by the formula -A-O—, a group represented by the formula-A-O—B—, a group represented by the formula -[A-C(═O)—O]_(m)-B- and agroup represented by the formula -[A-O—C(═O)]_(m)—B—. Among these, agroup represented by the formula -[A-O—C(═O)]_(m)—B— is particularlydesirable. In the formulas, each of A and B independently represents adivalent aliphatic hydrocarbon group, and m represents an integer of 1to 3.

As the divalent aliphatic hydrocarbon group for A and B, the samedivalent aliphatic hydrocarbon groups as those described above for R⁸⁸can be mentioned.

As A, a linear or branched, divalent aliphatic hydrocarbon group ispreferable, a linear or branched alkylene group is preferable, a linearor branched alkylene group of 2 to 6 carbon atoms is still morepreferable, an ethylene group or an alkylethylene group is still morepreferable, and an ethylene group is most preferable.

The alkyl group within the alkylethylene group is preferably a linearalkyl group of 1 to 5 carbon atoms, more preferably a linear alkyl groupof 1 to 3 carbon atoms, and most preferably a methyl group.

As B, a linear or branched, divalent aliphatic hydrocarbon group ispreferable, a linear or branched alkylene group is preferable, a linearor branched alkylene group of 2 to 6 carbon atoms is still morepreferable, an ethylene group or an alkylethylene group is still morepreferable, and an ethylene group is most preferable.

The alkyl group within the alkylethylene group is preferably a linearalkyl group of 1 to 5 carbon atoms, more preferably a linear alkyl groupof 1 to 3 carbon atoms, and most preferably a methyl group.

In the group represented by the formula -[A-C(═O)—O]_(m)—B—, mrepresents an integer of 1 to 3, preferably 1 or 2, and most preferably1.

In the present invention, as the structural unit (a5), a structural unitrepresented by general formula (a5-1-11) shown below is particularlydesirable.

In the formula, each of a″ and b″ independently represents an integer of1 to 3.

In general formula (a5-1-11), a″ represents an integer of 1 to 3,preferably 2.

In general formula (a5-1-11), b″ represents an integer of 1 to 3, andpreferably 2.

As the structural unit (a5), one type of structural unit may be usedalone, or two or more types of structural units may be used incombination.

In terms of achieving excellent properties with respect to the shape ofa formed resist pattern, line width roughness (LWR), compatibility withthe substrate and the like in the formation of a resist pattern using apositive resist composition containing the component (A1), the amount ofthe structural unit (a5) within the component (A1), based on thecombined total of all structural units constituting the component (A1)is preferably 1 mol % or more, more preferably 5 to 35 mol %, still morepreferably 5 to 30 mol %, and most preferably 5 to 25 mol %.

The component (A1) is a polymeric compound including the structural unit(a1). Examples of the component (A1) include

a polymer consisting of the structural unit (a1);

a copolymer consisting of the structural units (a1) and (a3);

a copolymer consisting of the structural units (a1), (a3) and (a5);

a copolymer consisting of the structural units (a1), (a2) and (a3);

a copolymer consisting of the structural units (a0), (a1), (a2) and(a3);

a copolymer consisting of the structural units (a0), (a1), (a2) and(a5);

a copolymer consisting of the structural units (a0), (a1), (a3) and(a5); and

a copolymer consisting of the structural units (a0), (a1), (a2), (a3)and (a5).

In the present invention, as the component (A1), a copolymer thatincludes a combination of structural units such as that shown below(polymeric compounds (A1-1) to (A1-3)) is particularly desirable.

In the formula, R, R⁰², A′, R¹⁴, v and w are the same as defined above,wherein the plurality of R may be the same or different from each other;and R²⁰ represents an alkyl group, and examples thereof include the samealkyl groups as those described above for R¹⁴.

In the formula, R, A′, R¹⁴, v and w are the same as defined above,wherein the plurality of R may be the same or different from each other;R²⁰ represents an alkyl group, and examples thereof include the samealkyl groups as those described above for R¹⁴; R²⁹ represents a singlebond or a divalent linking group; and s″ represents an integer of 0 to2.

In the formula, R and R⁵¹ are the same as defined above, wherein theplurality of R may be the same or different from each other; R²⁹represents a single bond or a divalent linking group; s″ represents aninteger of 0 to 2; and h represents an integer of 1 to 6.

In the aforementioned chemical formulas representing the polymericcompounds (A1-1) to (A1-3), as the alkyl group for R²⁰, the same alkylgroups as those described above for R¹⁴ can be mentioned, and ispreferably a linear or branched alkyl group. As the linear alkyl group,a methyl group or an ethyl group is preferable. As the branched alkylgroup, an isopropyl group is particularly desirable.

In the chemical formulas, the alkyl group for R⁵¹ is the same as definedfor the alkyl group of 1 to 5 carbon atoms represented by R, preferablya methyl group or an ethyl group, and most preferably a methyl group.

In the chemical formulas, A′ is the same as defined for A′ in generalformula (a0-1-11), and is preferably an oxygen atom, a methylene groupor an ethylene group.

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (A1)is not particularly limited, but is preferably 1,000 to 50,000, morepreferably 1,500 to 30,000, and most preferably 2,500 to 20,000. Whenthe weight average molecular weight is no more than the upper limit ofthe above-mentioned range, the resist composition exhibits asatisfactory solubility in a resist solvent. On the other hand, when theweight average molecular weight is at least as large as the lower limitof the above-mentioned range, dry etching resistance and thecross-sectional shape of the resist pattern becomes satisfactory.

Further, the dispersity (Mw/Mn) is preferably 1.0 to 5.0, morepreferably 1.0 to 3.0, and most preferably 1.2 to 2.5. Here, Mn is thenumber average molecular weight.

In the component (A), as the component (A1), one type may be used alone,or two or more types may be used in combination.

In the component (A), the amount of the component (A1) based on thetotal weight of the component (A) is preferably 25% by weight or more,more preferably 50% by weight or more, still more preferably 75% byweight or more, and may be even 100% by weight. When the amount of thecomponent (A1) is 25% by weight or more, various lithography propertiesare improved. Further, the solubility of the base component (A) in anorganic solvent can be improved.

The component (A1) can be obtained, for example, by a conventionalradical polymerization or the like of the monomers corresponding witheach of the structural units, using a radical polymerization initiatorsuch as azobisisobutyronitrile (AIBN).

Furthermore, in the component (A1), by using a chain transfer agent suchas HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introduced atthe terminals of the component (A1). Such a copolymer having introduceda hydroxyalkyl group in which some of the hydrogen atoms of the alkylgroup are substituted with fluorine atoms is effective in reducingdeveloping defects and LER (line edge roughness: unevenness of the sidewalls of a line pattern).

As the monomers for deriving the corresponding structural units,commercially available monomers may be used, or the monomers may besynthesized by a conventional method.

For example, as a monomer for deriving the structural unit (a0), acompound represented by general formula (a0-1-0) shown below (hereafter,referred to as “compound (a0-1-0)”) can be used.

In general formula (a0-1-0), R, R² and R³ are the same as defined above.

The method for producing the compound (a0-1-0) is not particularlylimited, and the compound (a0-1-0) can be produced by a conventionalmethod.

For example, in the presence of a base, a compound (X-2) represented bygeneral formula (X-2) shown below is added to a solution obtained bydissolving a compound (X-1) represented by general formula (X-1) shownbelow in a reaction solvent, and a reaction is effected to therebyobtain a compound (a0-1-0).

Examples of the base include inorganic bases such as sodium hydride,K₂CO₃ and Cs₂CO₃; and organic bases such as triethylamine,4-dimethylaminopyridine (DMAP) and pyridine. Examples of condensingagents include carbodiimide reagents such asethyldiisopropylaminocarbodiimide hydrochloride (EDCI),dicyclohexylcarboxylmide (DCC), diisopropylcarbodiimide andcarbodiimidazole; tetraethyl pyrophosphate; andbenzotriazole-N-hydroxytrisdimethylaminophosphonium hexafluorophosphide(Bop reagent).

If desired, an acid may be used. As the acid, any acid generally usedfor dehydration/condensation may be used. Specific examples includeinorganic acids such as hydrochloric acid, sulfuric acid and phosphoricacid; and organic acids such as methanesulfonic acid,trifluoromethanesulfonic acid, benzenesulfonic acid andp-toluenesulfonic acid. These acids can be used individually, or in acombination of two or more.

[Component (A2)]

In the positive resist composition of the present invention, thecomponent (A) may contain “a base component which exhibits increasedsolubility in an alkali developing solution under action of acid” otherthan the component (A1) (hereafter, referred to as “component (A2)”).

The component (A2) is not particularly limited, and any of the multitudeof conventional base components used within chemically amplified resistcompositions (e.g., base resins used within chemically amplified resistcompositions for ArF excimer lasers or KrF excimer lasers, preferablyArF excimer lasers) can be used. For example, as a base resin for ArFexcimer laser, a base resin having the aforementioned structural unit(a1) as an essential component, and optionally the aforementionedstructural units (a2) to (a4) can be used. Further, the component (A2)may contain a non-polymer (low molecular weight compound) having amolecular weight of 500 to less than 4,000.

(Low-Molecular Weight Compound)

In the positive resist composition of the present invention, as thelow-molecular weight compound, it is preferable to use a compound thathas a molecular weight of at least 500 and less than 2,000, contains ahydrophilic group, and also contains an acid dissociable, dissolutioninhibiting group described above in connection with the structural unit(a1). Specific examples include compounds containing a plurality ofphenol skeletons in which a part of the hydrogen atoms within hydroxylgroups have been substituted with the aforementioned acid dissociable,dissolution inhibiting groups.

Examples of the low-molecular weight compound include low molecularweight phenolic compounds in which a portion of the hydroxyl grouphydrogen atoms have been substituted with an aforementioned aciddissociable, dissolution inhibiting group, and these types of compoundsare known, for example, as sensitizers or heat resistance improvers foruse in non-chemically amplified g-line or i-line resists.

Examples of these low molecular weight phenol compounds includebis(4-hydroxyphenyl)methane, bis(2,3,4-trihydroxyphenyl)methane,2-(4-hydroxyphenyl)-2-(4′-hydroxyphenyl)propane,2-(2,3,4-trihydroxyphenyl)-2-(2′,3′,4′-trihydroxyphenyl)propane,tris(4-hydroxyphenyl)methane,bis(4-hydroxy-3,5-dimethylphenyl)-2-hydroxyphenylmethane,bis(4-hydroxy-2,5-dimethylphenyl)-2-hydroxyphenylmethane,bis(4-hydroxy-3,5-dimethylphenyl)-3,4-dihydroxyphenylmethane,bis(4-hydroxy-2,5-dimethylphenyl)-3,4-dihydroxyphenylmethane,bis(4-hydroxy-3-methylphenyl)-3,4-dihydroxyphenylmethane,bis(3-cyclohexyl-4-hydroxy-6-methylphenyl)-4-hydroxyphenylmethane,bis(3-cyclohexyl-4-hydroxy-6-methylphenyl)-3,4-dihydroxyphenylmethane,1-[1-(4-hydroxyphenyl)isopropyl]-4-[1,1-bis(4-hydroxyphenyl)ethyl]benzene,and dimers, trimers and tetramers of formalin condensation products ofphenols such as phenol, m-cresol, p-cresol and xylenol. Needless to say,the low molecular weight phenol compound is not limited to theseexamples.

Also, there are no particular limitations on the acid dissociable,dissolution inhibiting group, and suitable examples include the groupsdescribed above.

As the component (A2), one type of resin may be used, or two or moretypes of resins may be used in combination.

In the positive resist composition of the present invention, as thecomponent (A), one type may be used, or two or more types of compoundsmay be used in combination.

In the positive resist composition of the present invention, the amountof the component (A) can be appropriately adjusted depending on thethickness of the resist film to be formed, and the like.

<Component (B)>

In the present invention, as the component (B), there is no particularlimitation, and any of the known acid generators used in conventionalchemically amplified resist compositions can be used.

Examples of these acid generators are numerous, and include onium saltacid generators such as iodonium salts and sulfonium salts; oximesulfonate acid generators; diazomethane acid generators such as bisalkylor bisaryl sulfonyl diazomethanes and poly(bis-sulfonyl)diazomethanes;nitrobenzylsulfonate acid generators; iminosulfonate acid generators;and disulfone acid generators.

As an onium salt acid generator, a compound represented by generalformula (b-1) or (b-2) shown below can be used.

In the formulas above, R¹″ to R³″, R⁵″ and R⁶″ each independentlyrepresent an aryl group or alkyl group, wherein two of R¹″ to R³″ may bebonded to each other to form a ring with the sulfur atom; and R⁴″represents an alkyl group, a halogenated alkyl group, an aryl group oran alkenyl group which may have a substituent, with the provision thatat least one of R¹″ to R³″ represents an aryl group, and at least one ofR⁵″ and R⁶″ represents an aryl group.

In formula (b-1), R¹″ to R³″ each independently represents an aryl groupor an alkyl group. In formula (b-1), two of R¹″ to R³″ may be bonded toeach other to form a ring with the sulfur atom.

Further, among R¹″ to R³″, at least one group represents an aryl group.Among R¹″ to R³″, two or more groups are preferably aryl groups, and itis particularly desirable that all of R¹″ to R³″ are aryl groups.

The aryl group for R¹″ to R³″ is not particularly limited. For example,an aryl group having 6 to 20 carbon atoms may be used in which part orall of the hydrogen atoms of the aryl group may or may not besubstituted with alkyl groups, alkoxy groups, halogen atoms or hydroxylgroups.

Further, at least one of R¹″ to R³″ may be an aryl group having asubstituent represented by general formula (b1-0) shown below.

In general formula (b1-0), R^(C) represents a chain-like or cyclichydrocarbon group; f represents 0 or 1; and g represents 0 or 1.

The aryl group is preferably an aryl group having 6 to 10 carbon atomsbecause it can be synthesized at a low cost. Specific examples thereofinclude a phenyl group and a naphthyl group.

The alkyl group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkyl group having 1 to 5 carbon atoms,and most preferably a methyl group, an ethyl group, a propyl group, ann-butyl group, or a tert-butyl group.

The alkoxy group, with which hydrogen atoms of the aryl group may besubstituted, is preferably an alkoxy group having 1 to 5 carbon atoms,more preferably a methoxy group, an ethoxy group, an n-propoxy group, aniso-propoxy group, an n-butoxy group or a tert-butoxy group, and mostpreferably a methoxy group or an ethoxy group.

The halogen atom, with which hydrogen atoms of the aryl group may besubstituted, is preferably a fluorine atom.

In general formula (b1-0), R^(C) represents a chain-like or cyclichydrocarbon group.

With respect to R^(C), the hydrocarbon group may be either an aromatichydrocarbon group or an aliphatic hydrocarbon group.

Examples of the aliphatic hydrocarbon group for R^(C) include a linear,branched or cyclic, saturated hydrocarbon group of 1 to 15 carbon atomsand a linear, branched or cyclic, unsaturated hydrocarbon group of 2 to5 carbon atoms.

Examples of the linear, saturated hydrocarbon group include a methylgroup, an ethyl group, a propyl group, a butyl group, a pentyl group, ahexyl group, a heptyl group, an octyl group, a nonyl group and a decylgroup.

Examples of the branched, saturated hydrocarbon group include a1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group anda tert-butyl group.

The linear or branched, saturated hydrocarbon group may have asubstituent. Examples of the substituent include an alkoxy group, ahalogen atom, a hydroxyl group, an oxygen atom (═O), a cyano group and acarboxy group.

The alkoxy group as the substituent for the linear or branched,saturated alkyl group is preferably an alkoxy group having 1 to 5 carbonatoms, more preferably a methoxy group, an ethoxy group, an n-propoxygroup, an iso-propoxy group, an n-butoxy group or a tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the linear orbranched, saturated alkyl group include a fluorine atom, a chlorineatom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

The cyclic, saturated hydrocarbon group may be either a polycyclic groupor a monocyclic group. Examples thereof include cyclic, saturatedhydrocarbon groups of 3 to 20 carbon atoms, such as groups in which onehydrogen atom has been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, a tricycloalkane or atetracycloalkane. More specific examples include groups in which onehydrogen atom has been removed from a monocycloalkane such ascyclopentane, cyclohexane, cycloheptane or cyclooctane; and groups inwhich one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane.

The cyclic, saturated hydrocarbon group may have a substituent. As thecyclic, saturated group having a substituent, for example, part of thecarbon atoms constituting the ring within the cyclic, saturatedhydrocarbon group may be substituted with a hetero atom (formerexample), or a hydrogen atom bonded to the ring within the cyclic,saturated hydrocarbon group may be substituted with a substituent(latter example).

In the former example, a heterocycloalkane in which part of the carbonatoms constituting the ring within the aforementioned monocycloalkane orpolycycloalkane has been substituted with a hetero atom such as anoxygen atom, a sulfur atom or a nitrogen atom, and one hydrogen atom hasbeen removed therefrom, can be used. Further, the ring may contain anester bond (—C(═O)—O—). More specific examples include alactone-containing monocyclic group, such as a group in which onehydrogen atom has been removed from γ-butyrolactone; and alactone-containing polycyclic group, such as a group in which onehydrogen atom has been removed from a bicycloalkane, tricycloalkane ortetracycloalkane containing a lactone ring.

In the latter example, as the substituent, the same substituent groupsas those for the aforementioned linear or branched, saturatedhydrocarbon group, or an alkyl group can be used. The alkyl group as thesubstituent is preferably an alkyl group of 1 to 5 carbon atoms, andmore preferably a methyl group or an ethyl group. The carbon atom whichconstitutes the ring and has the alkyl group bonded thereto ispreferably bonded to the terminal of —C(═O)—(O)g- within the substituentrepresented by general formula (b1-0).

Examples of the linear, unsaturated hydrocarbon group for R^(C) includea vinyl group, a propenyl group (an allyl group) and a butynyl group.

Examples of branched unsaturated hydrocarbon groups include a1-methylpropenyl group and a 2-methylpropenyl group.

The aforementioned linear or branched, unsaturated hydrocarbon group mayhave a substituent. Examples of substituents include the samesubstituents as those which the aforementioned linear or branched,saturated hydrocarbon group may have.

The aromatic hydrocarbon group for R^(C) may be either a group includingan aromatic hydrocarbon ring in which the ring skeleton of the aromaticring is constituted of only carbon atoms, or a group including anaromatic hetero ring in which the ring skeleton of the aromatic ringcontains not only carbon atoms but also a hetero atom.

Specific examples include an aryl group in which one hydrogen atom hasbeen removed from an aromatic hydrocarbon ring, such as a phenyl group,a biphenyl group, a fluorenyl group, a naphthyl group, an anthryl groupor a phenanthryl group; a heteroaryl group in which part of the carbonatoms constituting the ring of the aforementioned aryl group has beensubstituted with a hetero atom such as an oxygen atom, a sulfur atom ora nitrogen atom; and an arylalkyl group, such as a benzyl group, aphenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a1-naphthylethyl group or a 2-naphthylethyl group. The alkyl chain withinthe arylalkyl group preferably has 1 to 4 carbon atom, more preferably 1or 2, and most preferably 1.

The aromatic hydrocarbon group may have a substituent. As the aromatichydrocarbon group having a substituent, for example, part of the carbonatoms constituting the aromatic ring within the aromatic hydrocarbongroup may be substituted with a hetero atom, or a hydrogen atom bondedto the aromatic ring within the aromatic hydrocarbon group may besubstituted with a substituent.

In the former example, a heteroaryl group in which part of the carbonatoms constituting the ring within the aforementioned aryl group hasbeen substituted with a hetero atom such as an oxygen atom, a sulfuratom or a nitrogen atom, and a heteroarylalkyl group in which part ofthe carbon atoms constituting the ring of the aforementioned arylalkylgroup has been substituted with the aforementioned heteroatom can beused.

In the latter example, as the substituent for the cyclic alkyl group, analkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group,a hydroxyl group, an oxygen atom (═O) or the like can be used.

The alkyl group as the substituent for the aromatic hydrocarbon group ispreferably an alkyl group of 1 to 5 carbon atoms, and more preferably amethyl group, an ethyl group, a propyl group, an n-butyl group or atert-butyl group.

The alkoxy group as the substituent for the aromatic hydrocarbon groupis preferably an alkoxy group having 1 to 5 carbon atoms, morepreferably a methoxy group, an ethoxy group, an n-propoxy group, aniso-propoxy group, an n-butoxy group or a tert-butoxy group, and mostpreferably a methoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the aromatichydrocarbon group include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is preferable.

Example of the halogenated alkyl group as the substituent for thearomatic hydrocarbon group includes a group in which part or all of thehydrogen atoms within the aforementioned alkyl group have beensubstituted with the aforementioned halogen atoms.

Among the aforementioned examples, as R^(C), a cyclic hydrocarbon groupis preferable, a cyclic aliphatic hydrocarbon is more preferable, and agroup in which one hydrogen atom has been removed from adamantane, agroup in which one hydrogen atom has been removed from cyclopentane, ora group in which one hydrogen atom has been removed from cyclohexane isparticularly desirable.

It is also preferable that R^(C) represent a linear or branched,saturated hydrocarbon group which may have a substituent, and afluorinated alkyl group is particularly desirable.

In general formula (b1-0), f represents 0 or 1.

In general formula (b1-0), g represents 0 or 1.

The alkyl group for R¹″ to R³″ is not particularly limited and includes,for example, a linear, branched or cyclic alkyl group having 1 to 10carbon atoms. In terms of achieving excellent resolution, the alkylgroup preferably has 1 to 5 carbon atoms. Specific examples thereofinclude a methyl group, an ethyl group, an n-propyl group, an isopropylgroup, an n-butyl group, an isobutyl group, an n-pentyl group, acyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group, anda decyl group, and a methyl group is most preferable because it isexcellent in resolution and can be synthesized at a low cost.

When two of R¹″ to R³″ in formula (b-1) are bonded to each other to forma ring with the sulfur atom, it is preferable that the two of R¹″ to R³″form a 3 to 10-membered ring including the sulfur atom, and it isparticularly desirable that the two of R¹″ to R³″ form a 5 to 7-memberedring including the sulfur atom.

When two of R¹″ to R³″ in formula (b-1) are bonded to each other to forma ring with the sulfur atom, the remaining one of R¹″ to R³″ ispreferably an aryl group. As examples of the aryl group, the same as theabove-mentioned aryl groups for R¹″ to R³″ can be given.

Specific examples of preferable cation moieties for the compoundrepresented by general formula (b-1) are shown below. Among theexamples, those which have a triphenylmethane skeleton are preferable.

In formulas (1-1-7) and (1-1-8), each of R⁹ and R¹⁰ independentlyrepresents a phenyl group or naphthyl group which may have asubstituent, an alkyl group of 1 to 5 carbon atoms, an alkoxy group or ahydroxy group.

u is an integer of 1 to 3, and most preferably 1 or 2.

R⁴″ represents an alkyl group, a halogenated alkyl group, an aryl groupor an alkenyl group which may have a substituent.

The alkyl group for R⁴″ may be any of linear, branched or cyclic.

The linear or branched alkyl group preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbonatoms.

The cyclic alkyl group preferably has 4 to 15 carbon atoms, morepreferably 4 to 10 carbon atoms, and most preferably 6 to 10 carbonatoms.

As an example of the halogenated alkyl group for R⁴″, a group in whichpart of or all of the hydrogen atoms of the aforementioned linear,branched or cyclic alkyl group have been substituted with halogen atomscan be given. Examples of the aforementioned halogen atom include afluorine atom, a chlorine atom, a bromine atom and an iodine atom, and afluorine atom is preferable.

In the halogenated alkyl group, the percentage of the number of halogenatoms based on the total number of halogen atoms and hydrogen atoms(halogenation ratio (%)) is preferably 10 to 100%, more preferably 50 to100%, and most preferably 100%. Higher halogenation ratios arepreferable, as they result in increased acid strength.

The aryl group for R⁴″ is preferably an aryl group of 6 to 20 carbonatoms.

The alkenyl group for R⁴″ is preferably an alkenyl group of 2 to 10carbon atoms.

With respect to R⁴″, the expression “may have a substituent” means thatpart of or all of the hydrogen atoms within the aforementioned linear,branched or cyclic alkyl group, halogenated alkyl group, aryl group oralkenyl group may be substituted with substituents (atoms other thanhydrogen atoms, or groups).

R⁴″ may have one substituent, or two or more substituents.

Examples of the substituent include a halogen atom, a hetero atom, analkyl group, and a group represented by the formula X-Q²- (in theformula, Q² represents a divalent linking group containing an oxygenatom; and X represents a hydrocarbon group of 3 to 30 carbon atoms whichmay have a substituent).

Examples of halogen atoms and alkyl groups as substituents for R⁴″include the same halogen atoms and alkyl groups as those described abovewith respect to the halogenated alkyl group for R⁴″.

Examples of hetero atoms include an oxygen atom, a nitrogen atom, and asulfur atom.

In the group represented by formula X-Q²-, Q² represents a divalentlinking group containing an oxygen atom.

Q² may contain an atom other than an oxygen atom. Examples of atomsother than oxygen include a carbon atom, a hydrogen atom, a sulfur atomand a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom includenon-hydrocarbon, oxygen atom-containing linking groups such as an oxygenatom (an ether bond; —O—), an ester bond (—C(═O)—O—), an amido bond(—C(═O)—NH—), a carbonyl group (—C(═O)—) and a carbonate bond(—O—C(═O)—O—); and combinations of the aforementioned non-hydrocarbon,hetero atom-containing linking groups with an alkylene group.

Specific examples of the combinations of the aforementionednon-hydrocarbon, hetero atom-containing linking groups and an alkylenegroup include —R⁹¹—O—, —R⁹²—O—C(═O)—, —C(═O)—O—R⁹³—O—C(═O)— (in theformulas, each of R⁹¹ to R⁹³ independently represents an alkylenegroup).

The alkylene group for R⁹¹ to R⁹³ is preferably a linear or branchedalkylene group, and preferably has 1 to 12 carbon atoms, more preferably1 to 5, and most preferably 1 to 3.

Specific examples of alkylene groups include a methylene group [—CH₂—];alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—,—C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and —C(CH₂CH₃)₂—; an ethylenegroup [—CH₂CH₂—]; alkylethylene groups such as —CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—; a trimethylene group(n-propylene group) [—CH₂CH₂CH₂—]; alkyltrimethylene groups such as—CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; a tetramethylene group[—CH₂CH₂CH₂CH₂—]; alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—and —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group [—CH₂CH₂CH₂CH₂CH₂—].

As Q², a divalent linking group containing an ester bond or an etherbond is preferable, and —R⁹¹—O—, —R⁹²—O—C(═O)— or —C(═O)—O—R⁹³—O—C(═O)—is more preferable.

In the group represented by the formula X-Q²-, the hydrocarbon group forX may be either an aromatic hydrocarbon group or an aliphatichydrocarbon group.

The aromatic hydrocarbon group is a hydrocarbon group having an aromaticring. The aromatic hydrocarbon ring preferably has 3 to 30 carbon atoms,more preferably 5 to 30, still more preferably 5 to 20, still morepreferably 6 to 15, and most preferably 6 to 12. Here, the number ofcarbon atoms within a substituent(s) is not included in the number ofcarbon atoms of the aromatic hydrocarbon group.

Specific examples of aromatic hydrocarbon groups include an aryl groupwhich is an aromatic hydrocarbon ring having one hydrogen atom removedtherefrom, such as a phenyl group, a biphenyl group, a fluorenyl group,a naphthyl group, an anthryl group or a phenanthryl group; and analkylaryl group such as a benzyl group, a phenethyl group, a1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethylgroup, or a 2-naphthylethyl group. The alkyl chain within the arylalkylgroup preferably has 1 to 4 carbon atom, more preferably 1 or 2, andmost preferably 1.

The aromatic hydrocarbon group may have a substituent. For example, partof the carbon atoms constituting the aromatic ring within the aromatichydrocarbon group may be substituted with a hetero atom, or a hydrogenatom bonded to the aromatic ring within the aromatic hydrocarbon groupmay be substituted with a substituent.

In the former example, a heteroaryl group in which part of the carbonatoms constituting the ring within the aforementioned aryl group hasbeen substituted with a hetero atom such as an oxygen atom, a sulfuratom or a nitrogen atom, and a heteroarylalkyl group in which part ofthe carbon atoms constituting the aromatic hydrocarbon ring within theaforementioned arylalkyl group has been substituted with theaforementioned heteroatom can be used.

In the latter example, as the substituent for the aromatic hydrocarbongroup, an alkyl group, an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) or the like can beused.

The alkyl group as the substituent for the aromatic hydrocarbon group ispreferably an alkyl group of 1 to 5 carbon atoms, and a methyl group, anethyl group, a propyl group, an n-butyl group or a tert-butyl group isparticularly desirable.

The alkoxy group as the substituent for the aromatic hydrocarbon groupis preferably an alkoxy group having 1 to 5 carbon atoms, morepreferably a methoxy group, ethoxy group, n-propoxy group, iso-propoxygroup, n-butoxy group or tert-butoxy group, and most preferably amethoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the aromatichydrocarbon group include a fluorine atom, a chlorine atom, a bromineatom and an iodine atom, and a fluorine atom is preferable.

Example of the halogenated alkyl group as the substituent for thearomatic hydrocarbon group includes a group in which part or all of thehydrogen atoms within the aforementioned alkyl group have beensubstituted with the aforementioned halogen atoms.

The aliphatic hydrocarbon group for X may be either a saturatedaliphatic hydrocarbon group, or an unsaturated aliphatic hydrocarbongroup. Further, the aliphatic hydrocarbon group may be linear, branchedor cyclic.

In the aliphatic hydrocarbon group for X, part of the carbon atomsconstituting the aliphatic hydrocarbon group may be substituted with asubstituent group containing a hetero atom, or part or all of thehydrogen atoms constituting the aliphatic hydrocarbon group may besubstituted with a substituent group containing a hetero atom.

As the “hetero atom” for X, there is no particular limitation as long asit is an atom other than carbon and hydrogen. Examples of hetero atomsinclude a halogen atom, an oxygen atom, a sulfur atom and a nitrogenatom. Examples of the halogen atom include a fluorine atom, a chlorineatom, an iodine atom and a bromine atom.

The substituent group containing a hetero atom may consist of a heteroatom, or may be a group containing a group or atom other than a heteroatom.

Specific examples of the substituent group for substituting part of thecarbon atoms include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—,—NH— (the H may be replaced with a substituent such as an alkyl group oran acyl group), —S—, —S(═O)₂— and —S(═O)₂—O—. When the aliphatichydrocarbon group is cyclic, the aliphatic hydrocarbon group may containany of these substituent groups in the ring structure.

Examples of the substituent group for substituting part or all of thehydrogen atoms include an alkoxy group, a halogen atom, a halogenatedalkyl group, a hydroxyl group, an oxygen atom (═O) and a cyano group.

The aforementioned alkoxy group is preferably an alkoxy group having 1to 5 carbon atoms, more preferably a methoxy group, ethoxy group,n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group,and most preferably a methoxy group or an ethoxy group.

Examples of the aforementioned halogen atom include a fluorine atom, achlorine atom, a bromine atom and an iodine atom, and a fluorine atom ispreferable.

Example of the aforementioned halogenated alkyl group includes a groupin which part or all of the hydrogen atoms within an alkyl group of 1 to5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, ann-butyl group or a tert-butyl group) have been substituted with theaforementioned halogen atoms.

As the aliphatic hydrocarbon group, a linear or branched saturatedhydrocarbon group, a linear or branched monovalent unsaturatedhydrocarbon group, or a cyclic aliphatic hydrocarbon group (aliphaticcyclic group) is preferable.

The linear saturated hydrocarbon group (alkyl group) preferably has 1 to20 carbon atoms, more preferably 1 to 15, and most preferably 1 to 10.Specific examples include a methyl group, an ethyl group, a propylgroup, a butyl group, a pentyl group, a hexyl group, a heptyl group, anoctyl group, a nonyl group, a decyl group, an undecyl group, a dodecylgroup, a tridecyl group, an isotridecyl group, a tetradecyl group, apentadecyl group, a hexadecyl group, an isohexadecyl group, a heptadecylgroup, an octadecyl group, a nonadecyl group, an icosyl group, ahenicosyl group and a docosyl group.

The branched saturated hydrocarbon group (alkyl group) preferably has 3to 20 carbon atoms, more preferably 3 to 15, and most preferably 3 to10. Specific examples include a 1-methylethyl group, a 1-methylpropylgroup, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutylgroup, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutylgroup, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentylgroup and a 4-methylpentyl group.

The unsaturated hydrocarbon group preferably has 2 to 10 carbon atoms,more preferably 2 to 5, still more preferably 2 to 4, and mostpreferably 3. Examples of linear monovalent unsaturated hydrocarbongroups include a vinyl group, a propenyl group (an allyl group) and abutynyl group. Examples of branched monovalent unsaturated hydrocarbongroups include a 1-methylpropenyl group and a 2-methylpropenyl group.

Among the above-mentioned examples, as the unsaturated hydrocarbongroup, a propenyl group is particularly desirable.

The aliphatic cyclic group may be either a monocyclic group or apolycyclic group. The aliphatic cyclic group preferably has 3 to 30carbon atoms, more preferably 5 to 30, still more preferably 5 to 20,still more preferably 6 to 15, and most preferably 6 to 12.

As the aliphatic cyclic group, a group in which one or more hydrogenatoms have been removed from a monocycloalkane or a polycycloalkane suchas a bicycloalkane, tricycloalkane or tetracycloalkane can be used.Specific examples include groups in which one or more hydrogen atomshave been removed from a monocycloalkane such as cyclopentane orcyclohexane; and groups in which one or more hydrogen atoms have beenremoved from a polycycloalkane such as adamantane, norbornane,isobornane, tricyclodecane or tetracyclododecane.

When the aliphatic cyclic group does not contain a heteroatom-containing substituent group in the ring structure thereof, thealiphatic cyclic group is preferably a polycyclic group, more preferablya group in which one or more hydrogen atoms have been removed from apolycycloalkane, and a group in which one or more hydrogen atoms havebeen removed from adamantane is particularly desirable.

When the aliphatic cyclic group contains a hetero atom-containingsubstituent group in the ring structure thereof, the heteroatom-containing substituent group is preferably —O—, —C(═O)—O—, —S—,—S(═O)₂— or —S(═O)₂—O—. Specific examples of such aliphatic cyclicgroups include groups represented by formulas (L1) to (L5) and (S1) to(S4) shown below.

In the formula, Q″ represents an alkylene group of 1 to 5 carbon atoms,—O—, —S—, —O—R⁹⁴— or —S—R⁹⁵— (wherein each of R⁹⁴ and R⁹⁵ independentlyrepresents an alkylene group of 1 to 5 carbon atoms); and m represents 0or 1.

As the alkylene group for Q″, R⁹⁴ and R⁹⁵, the same alkylene groups asthose described above for R⁹¹ to R⁹³ can be used.

In these aliphatic cyclic groups, part of the hydrogen atoms bonded tothe carbon atoms constituting the ring structure may be substituted witha substituent. Examples of substituents include an alkyl group, analkoxy group, a halogen atom, a halogenated alkyl group, a hydroxylgroup and an oxygen atom (═O).

As the alkyl group, an alkyl group of 1 to 5 carbon atoms is preferable,and a methyl group, an ethyl group, a propyl group, an n-butyl group ora tert-butyl group is particularly desirable.

As the alkoxy group and the halogen atom, the same groups as thesubstituent groups for substituting part or all of the hydrogen atomscan be used.

Among the examples described above, as X, a cyclic group which may havea substituent is preferable. The cyclic group may be either an aromatichydrocarbon group which may have a substituent, or an aliphatic cyclicgroup which may have a substituent, and an aliphatic cyclic group whichmay have a substituent is preferable.

As the aromatic hydrocarbon group, a naphthyl group which may have asubstituent, or a phenyl group which may have a substituent ispreferable.

As the aliphatic cyclic group which may have a substituent, an aliphaticpolycyclic group which may have a substituent is preferable. As thealiphatic polycyclic group, the aforementioned group in which one ormore hydrogen atoms have been removed from a polycycloalkane, and groupsrepresented by the aforementioned formulas (L2) to (L5), (S3) and (S4)are preferable.

Further, in the present invention, X preferably has a structure similarto that of the R⁰³ group within the structural unit (a0) for thecomponent (A1), and a group having a polar portion is particularlydesirable, because it results in improved lithographic properties andresist pattern shape.

Specific examples of X having a polar moiety include those in which apart of the carbon atoms constituting the aliphatic hydrocarbon groupfor X is substituted with a substituent group containing a hetero atomsuch as —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH— (whereinH may be substituted with a substituent such as an alkyl group or anacyl group), —S—, —S(═O)₂— and —S(═O)₂—O—.

In the present invention, R⁴″ preferably has X-Q²- as a substituent. Inthis case, R⁴″ is preferably a group represented by formula X-Q²-Y³—[wherein Q² and X are the same as defined above; and Y³ represents analkylene group of 1 to 4 carbon atoms which may have a substituent, or afluorinated alkylene group of 1 to 4 carbon atoms which may have asubstituent].

In the group represented by the formula X-Q²-Y³—, as the alkylene groupfor Y³, the same alkylene group as those described above for Q² in whichthe number of carbon atoms is 1 to 4 can be used.

As the fluorinated alkylene group for Y³, the aforementioned alkylenegroup in which part or all of the hydrogen atoms has been substitutedwith fluorine atoms can be used.

Specific examples of Y³ include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—,—CF(CF₃)CF₂—, —CF(CF₂CF₃)—, —C(CF₃)₂—, —CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—,—CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—, —C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—,—CF(CF₂CF₂CF₃)—, —C(CF₃)(CF₂CF₃)—; —CHF—, —CH₂CF₂—, —CH₂CH₂CF₂—,—CH₂CF₂CF₂—, —CH(CF₃)CH₂—, —CH(CF₂CF₃)—, —C(CH₃)(CF₃)—, —CH₂CH₂CH₂CF₂—,—CH₂CH₂CF₂CF₂—, —CH(CF₃)CH₂CH₂—, —CH₂CH(CF₃)CH₂—, —CH(CF₃)CH(CF₃)—,—C(CF₃)₂CH₂—; —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —CH₂CH₂CH₂CH₂—, —CH(CH₃)CH₂CH₂—, —CH₂CH(CH₃)CH₂—,—CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, —CH(CH₂CH₂CH₃)—, and—C(CH₃)(CH₂CH₃)—.

Y³ is preferably a fluorinated alkylene group, and particularlypreferably a fluorinated alkylene group in which the carbon atom bondedto the adjacent sulfur atom is fluorinated. Examples of such fluorinatedalkylene groups include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—, —CF(CF₃)CF₂—,—CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—, —CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—,—C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—; —CH₂CF₂—, —CH₂CH₂CF₂—, —CH₂CF₂CF₂—;—CH₂CH₂CH₂CF₂—, —CH₂CH₂CF₂CF₂—, and —CH₂CF₂CF₂CF₂—.

Of these, —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂— or CH₂CF₂CF₂— is preferable,—CF₂—, —CF₂CF₂— or —CF₂CF₂CF₂— is more preferable, and —CF₂— isparticularly desirable.

The alkylene group or fluorinated alkylene group may have a substituent.The alkylene group or fluorinated alkylene group “has a substituent”means that part or all of the hydrogen atoms or fluorine atoms in thealkylene group or fluorinated alkylene group has been substituted withgroups other than hydrogen atoms and fluorine atoms.

Examples of substituents which the alkylene group or fluorinatedalkylene group may have include an alkyl group of 1 to 4 carbon atoms,an alkoxy group of 1 to 4 carbon atoms, and a hydroxyl group.

In formula (b-2), R⁵″ and R⁶″ each independently represent an aryl groupor alkyl group. At least one of R⁵″ and R⁶″ represents an aryl group. Itis preferable that both of R⁵″ and R⁶″ represent an aryl group.

As the aryl group for R⁵″ and R⁶″, the same as the aryl groups for R¹″to R³″ can be used.

As the alkyl group for R⁵″ and R⁶″, the same as the alkyl groups for R¹″to R³″ can be used.

It is particularly desirable that both of R⁵″ and R⁶″ represents aphenyl group.

As R⁴″ in formula (b-2), the same groups as those mentioned above forR⁴″ in formula (b-1) can be used.

Specific examples of suitable onium salt acid generators represented byformula (b-1) or (b-2) include diphenyliodoniumtrifluoromethanesulfonate or nonafluorobutanesulfonate;bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate ornonafluorobutanesulfonate; triphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-methylphenyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;dimethyl(4-hydroxynaphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;monophenyldimethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenylmonomethylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;(4-methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;tri(4-tert-butyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;diphenyl(1-(4-methoxy)naphthyl)sulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;di(1-naphthyl)phenylsulfonium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-phenyltetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(4-methylphenyl)tetrahydrothiophenium trifluoromethanesulfonate,heptafluoropropanesulfonate or nonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-methoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-ethoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(4-n-butoxynaphthalene-1-yl)tetrahydrothiopheniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-phenyltetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; 1-(4-hydroxyphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate;1-(3,5-dimethyl-4-hydroxyphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate; and 1-(4-methylphenyl)tetrahydrothiopyraniumtrifluoromethanesulfonate, heptafluoropropanesulfonate ornonafluorobutanesulfonate.

It is also possible to use onium salts in which the anion moiety ofthese onium salts are replaced by an alkylsulfonate such asmethanesulfonate, n-propanesulfonate, n-butanesulfonate, orn-octanesulfonate.

Further, onium salts in which the anion moiety of these onium salts isreplaced by an anion moiety represented by the chemical formula shownbelow which contains an alicyclic group can also be used.

Furthermore, onium salts in which the anion moiety of these onium saltsis replaced by an anion moiety represented by any one of formulas (b1)to (b8) shown below can also be used.

In the formulas, z0 represents an integer of 1 to 3; each of q1 and q2independently represents an integer of 1 to 5; q3 represents an integerof 1 to 12; t3 represents an integer of 1 to 3; each of r1 and r2independently represents an integer of 0 to 3; i represents an integerof 1 to 20; R⁷ represents a substituent; each of m1 to m5 independentlyrepresents 0 or 1; each of v0 to v5 independently represents an integerof 0 to 3; each of w1 to w5 independently represents an integer of 0 to3; and Q″ is the same as defined above.

As the substituent for R⁷, the same groups as those which theaforementioned aliphatic hydrocarbon group or aromatic hydrocarbon groupfor X may have as a substituent can be used.

If there are two or more of the R⁷ group, as indicated by the values r1,r2, and w1 to w5, then the two or more of the R⁷ groups may be the sameor different from each other.

Further, onium salt-based acid generators in which the anion moiety ingeneral formula (b-1) or (b-2) is replaced by an anion represented bygeneral formula (b-3) or (b-4) shown below (the cation moiety is thesame as (b-1) or (b-2)) may be used.

In the formulas, X″ represents an alkylene group of 2 to 6 carbon atomsin which at least one hydrogen atom has been substituted with a fluorineatom; and each of Y″ and Z″ independently represents an alkyl group of 1to 10 carbon atoms in which at least one hydrogen atom has beensubstituted with a fluorine atom.

X″ represents a linear or branched alkylene group in which at least onehydrogen atom has been substituted with a fluorine atom, and thealkylene group has 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms,and most preferably 3 carbon atoms.

Each of Y″ and Z″ independently represents a linear or branched alkylgroup in which at least one hydrogen atom has been substituted with afluorine atom, and the alkyl group has 1 to 10 carbon atoms, preferably1 to 7 carbon atoms, and most preferably 1 to 3 carbon atoms.

The smaller the number of carbon atoms of the alkylene group for X″ orthose of the alkyl group for Y″ and Z″ within the above-mentioned rangeof the number of carbon atoms, the more the solubility in a resistsolvent is improved.

Further, in the alkylene group for X″ or the alkyl group for Y″ and Z″,it is preferable that the number of hydrogen atoms substituted withfluorine atoms is as large as possible because the acid strengthincreases and the transparency to high energy radiation of 200 nm orless or electron beam is improved.

The fluorination ratio of the alkylene group or alkyl group ispreferably from 70 to 100%, more preferably from 90 to 100%, and it isparticularly desirable that the alkylene group or alkyl group be aperfluoroalkylene group or perfluoroalkyl group in which all hydrogenatoms are substituted with fluorine atoms.

Furthermore, as an onium salt-based acid generator, a sulfonium salthaving a cation moiety represented by general formula (b-5) or (b-6)shown below may be used.

In formulas (b-5) and (b-6) above, each of R⁸¹ to R⁸⁶ independentlyrepresents an alkyl group, an acetyl group, an alkoxy group, a carboxygroup, a hydroxyl group or a hydroxyalkyl group; each of n₁ to n₅independently represents an integer of 0 to 3; and n₆ represents aninteger of 0 to 2.

With respect to R⁸¹ to R⁸⁶, the alkyl group is preferably an alkyl groupof 1 to 5 carbon atoms, more preferably a linear or branched alkylgroup, and most preferably a methyl group, ethyl group, propyl group,isopropyl group, n-butyl group or tert butyl group.

The alkoxy group is preferably an alkoxy group of 1 to 5 carbon atoms,more preferably a linear or branched alkoxy group, and most preferably amethoxy group or ethoxy group.

The hydroxyalkyl group is preferably the aforementioned alkyl group inwhich one or more hydrogen atoms have been substituted with hydroxygroups, and examples thereof include a hydroxymethyl group, ahydroxyethyl group and a hydroxypropyl group.

If there are two or more of an individual R⁸¹ to R⁸⁶ group, as indicatedby the corresponding value of n₁ to n₆, then the two or more of theindividual R⁸¹ to R⁸⁶ group may be the same or different from eachother.

n₁ is preferably 0 to 2, more preferably 0 or 1, and still morepreferably 0.

It is preferable that n₂ and n₃ each independently represent 0 or 1, andmore preferably 0.

n₄ is preferably 0 to 2, and more preferably 0 or 1.

n₅ is preferably 0 or 1, and more preferably 0.

n₆ is preferably 0 or 1, and more preferably 1.

The anion moiety of the sulfonium salt having a cation moietyrepresented by general formula (b-5) or (b-6) is not particularlylimited, and the same anion moieties for onium salt-based acidgenerators which have been proposed may be used. Examples of such anionmoieties include fluorinated alkylsulfonic acid ions such as anionmoieties (R⁴″SO₃ ⁻) for onium salt-based acid generators represented bygeneral formula (b-1) or (b-2) shown above; and anion moietiesrepresented by general formula (b-3) or (b-4) shown above.

In the present description, an oximesulfonate acid generator is acompound having at least one group represented by general formula (B-1)shown below, and has a feature of generating acid by irradiation. Suchoximesulfonate acid generators are widely used for a chemicallyamplified resist composition, and can be appropriately selected.

In the formula, each of R³¹ and R³² independently represents an organicgroup.

The organic group for R³¹ and R³² refers to a group containing a carbonatom, and may include atoms other than carbon atoms (e.g., a hydrogenatom, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom(such as a fluorine atom and a chlorine atom) and the like).

As the organic group for R³¹, a linear, branched, or cyclic alkyl groupor aryl group is preferable. The alkyl group or the aryl group may havea substituent. The substituent is not particularly limited, and examplesthereof include a fluorine atom and a linear, branched, or cyclic alkylgroup having 1 to 6 carbon atoms. The alkyl group or the aryl group “hasa substituent” means that part or all of the hydrogen atoms of the alkylgroup or the aryl group is substituted with a substituent.

The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1to 10 carbon atoms, still more preferably 1 to 8 carbon atoms, stillmore preferably 1 to 6 carbon atoms, and most preferably 1 to 4 carbonatoms. As the alkyl group, a partially or completely halogenated alkylgroup (hereinafter, sometimes referred to as a “halogenated alkylgroup”) is particularly desirable. The “partially halogenated alkylgroup” refers to an alkyl group in which part of the hydrogen atoms aresubstituted with halogen atoms and the “completely halogenated alkylgroup” refers to an alkyl group in which all of the hydrogen atoms aresubstituted with halogen atoms. Examples of halogen atoms includefluorine atoms, chlorine atoms, bromine atoms and iodine atoms, andfluorine atoms are particularly desirable. In other words, thehalogenated alkyl group is preferably a fluorinated alkyl group.

The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the arylgroup, partially or completely halogenated aryl group is particularlydesirable. The “partially halogenated aryl group” refers to an arylgroup in which some of the hydrogen atoms are substituted with halogenatoms and the “completely halogenated aryl group” refers to an arylgroup in which all of hydrogen atoms are substituted with halogen atoms.

As R³¹, an alkyl group of 1 to 4 carbon atoms which has no substituentor a fluorinated alkyl group of 1 to 4 carbon atoms is particularlydesirable.

As the organic group for R³², a linear, branched, or cyclic alkyl group,aryl group, or cyano group is preferable. Examples of the alkyl groupand the aryl group for R³² include the same alkyl groups and aryl groupsas those described above for R³¹.

As R³², a cyano group, an alkyl group of 1 to 8 carbon atoms having nosubstituent or a fluorinated alkyl group of 1 to 8 carbon atoms isparticularly desirable.

Preferred examples of the oxime sulfonate acid generator includecompounds represented by general formula (B-2) or (B-3) shown below.

In the formula, R³³ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁴ represents an aryl group;and R³⁵ represents an alkyl group having no substituent or a halogenatedalkyl group.

In the formula, R³⁶ represents a cyano group, an alkyl group having nosubstituent or a halogenated alkyl group; R³⁷ represents a divalent ortrivalent aromatic hydrocarbon group; R³⁸ represents an alkyl grouphaving no substituent or a halogenated alkyl group; and p″ represents 2or 3.

In general formula (B-2), the alkyl group having no substituent or thehalogenated alkyl group for R³³ preferably has 1 to 10 carbon atoms,more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbonatoms.

As R³³, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

The fluorinated alkyl group for R³³ preferably has 50% or more of thehydrogen atoms thereof fluorinated, more preferably 70% or more, andmost preferably 90% or more.

Examples of the aryl group for R³⁴ include groups in which one hydrogenatom has been removed from an aromatic hydrocarbon ring, such as aphenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, ananthryl group, and a phenanthryl group, and heteroaryl groups in whichsome of the carbon atoms constituting the ring(s) of these groups aresubstituted with hetero atoms such as an oxygen atom, a sulfur atom, anda nitrogen atom. Of these, a fluorenyl group is preferable.

The aryl group for R³⁴ may have a substituent such as an alkyl group of1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. Thealkyl group and halogenated alkyl group as the substituent preferablyhas 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms.Further, the halogenated alkyl group is preferably a fluorinated alkylgroup.

The alkyl group having no substituent or the halogenated alkyl group forR³⁵ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbonatoms, and most preferably 1 to 6 carbon atoms.

As R³⁵, a halogenated alkyl group is preferable, and a fluorinated alkylgroup is more preferable.

In terms of enhancing the strength of the acid generated, thefluorinated alkyl group for R³⁵ preferably has 50% or more of thehydrogen atoms fluorinated, more preferably 70% or more, still morepreferably 90% or more. A completely fluorinated alkyl group in which100% of the hydrogen atoms are substituted with fluorine atoms isparticularly desirable.

In general formula (B-3), as the alkyl group having no substituent andthe halogenated alkyl group for R³⁶, the same alkyl group having nosubstituent and the halogenated alkyl group described above for R³³ canbe used.

Examples of the divalent or trivalent aromatic hydrocarbon group for R³⁷include groups in which one or two hydrogen atoms have been removed fromthe aryl group for R³⁴.

As the alkyl group having no substituent or the halogenated alkyl groupfor R³⁸, the same one as the alkyl group having no substituent or thehalogenated alkyl group for R³⁵ can be used.

p″ is preferably 2.

Specific examples of suitable oxime sulfonate acid generators includeα-(p-toluenesulfonyloxyimino)-benzyl cyanide,α-(p-chlorobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitrobenzenesulfonyloxyimino)-benzyl cyanide,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-benzyl cyanide,α-(benzenesulfonyloxyimino)-4-chlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,4-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-2,6-dichlorobenzyl cyanide,α-(benzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(2-chlorobenzenesulfonyloxyimino)-4-methoxybenzyl cyanide,α-(benzenesulfonyloxyimino)-thien-2-yl acetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)benzyl cyanide,α-[(p-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-(tosyloxyimino)-4-thienyl cyanide,α-(methylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cycloheptenyl acetonitrile,α-(methylsulfonyloxyimino)-1-cyclooctenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(ethylsulfonyloxyimino)-ethyl acetonitrile,α-(propylsulfonyloxyimino)-propyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclopentyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-cyclohexyl acetonitrile,α-(cyclohexylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclohexenyl acetonitrile,α-(methylsulfonyloxyimino)-phenyl acetonitrile,α-(methylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-phenyl acetonitrile,α-(trifluoromethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(ethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile,α-(propylsulfonyloxyimino)-p-methylphenyl acetonitrile, andα-(methylsulfonyloxyimino)-p-bromophenyl acetonitrile.

Further, oxime sulfonate acid generators disclosed in JapaneseUnexamined Patent Application, First Publication No. Hei 9-208554(Chemical Formulas 18 and 19 shown in paragraphs [0012] to [0014]) andoxime sulfonate acid generators disclosed in WO 2004/074242A2 (Examples1 to 40 described at pages 65 to 85) may be preferably used.

Furthermore, as preferable examples, the following can be used.

Of the aforementioned diazomethane acid generators, specific examples ofsuitable bisalkyl or bisaryl sulfonyl diazomethanes includebis(isopropylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane, andbis(2,4-dimethylphenylsulfonyl)diazomethane.

Further, diazomethane acid generators disclosed in Japanese UnexaminedPatent Application, First Publication No. Hei 11-035551, JapaneseUnexamined Patent Application, First Publication No. Hei 11-035552 andJapanese Unexamined Patent Application, First Publication No. Hei11-035573 may be preferably used.

Furthermore, as examples of poly(bis-sulfonyl)diazomethanes, thosedisclosed in Japanese Unexamined Patent Application, First PublicationNo. Hei 11-322707, including1,3-bis(phenylsulfonyldiazomethylsulfonyl)propane,1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane,1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane,1,10-bis(phenylsulfonyldiazomethylsulfonyl)decane,1,2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane,1,3-bis(cyclohexylsulfonyldiazomethylsulfonyl)propane,1,6-bis(cyclohexylsulfonyldiazomethylsulfonyl)hexane, and1,10-bis(cyclohexylsulfonyldiazomethylsulfonyl)decane, may be given.

As the component (B), one type of these acid generators may be usedalone, or two or more types may be used in combination.

In the present invention, as the component (B), it is preferable to usean onium salt having a fluorinated alkylsulfonic acid ion as the anionmoiety.

In the positive resist composition of the present invention, the amountof the component (B) relative to 100 parts by weight of the component(A) is preferably 0.5 to 50 parts by weight, and more preferably 1 to 40parts by weight. When the amount of the component (B) is within theabove-mentioned range, formation of a resist pattern can besatisfactorily performed. Further, by virtue of the above-mentionedrange, a uniform solution can be obtained and the storage stabilitybecomes satisfactory.

<Component (F)>[Structural Unit (f1)]

In the component (F), the structural unit (f1) has an “alkali developingsolution decomposable group” that is decomposable by an alkalideveloping solution. An “alkali developing solution decomposable group”refers to a group which is dissociated due to hydrolysis caused by theaction of an alkali developing solution generally used in the fields oflithography (e.g., a 2.38% by weight aqueous solution oftetramethylammonium hydroxide (TMAH) at 23° C.).

The alkali developing solution decomposable group is dissociated due tohydrolysis caused by the action of an alkali developing solution.Therefore, a hydrophilic group is formed when the alkali developingsolution decomposable group is dissociated and the hydrophilicity of thecomponent (F) is enhanced. As a result, the compatibility of thecomponent (F) with the alkali developing solution is improved.

The alkali developing solution decomposable group is not particularlylimited as long as it is an organic group that falls under thedefinition described above, and the alkali developing solutiondecomposable group may or may not contain a fluorine atom. In thestructural unit (f1), when no fluorine atom is contained in portionsother than the alkali developing solution decomposable group, it isnecessary that the alkali developing solution decomposable group containa fluorine atom. On the other hand, when a fluorine atom is contained ina portion other than the alkali developing solution decomposable group,the alkali developing solution decomposable group may or may not containa fluorine atom.

An alkali developing solution decomposable group containing a fluorineatom refers to an alkali developing solution decomposable group in whichpart or all of the hydrogen atoms have been substituted with a fluorineatom.

In the structural unit (f1), it is preferable that the alkali developingsolution decomposable group contains a fluorine atom. It is particularlydesirable that the fluorine atom contained in the structural unit (f1)is present only in the alkali developing solution decomposable group. Ifthe alkali developing solution decomposable group contains a fluorineatom, since the fluorine atom contained in the alkali developingsolution decomposable group is also dissociated from the structural unit(f1) when the alkali developing solution decomposable group isdissociated by the action of an alkali developing solution, the affinityfor the alkali developing solution is enhanced.

Specific examples of alkali developing solution decomposable groupscontaining a fluorine atom include those represented by general formulas(II-1) to (II-4) shown below. In the present invention, the alkalideveloping solution decomposable group is preferably at least one alkalideveloping solution decomposable group selected from those representedby general formulas (II-1) to (II-4) shown below. In terms of theeffects of the present invention and ease in synthesis, a grouprepresented by general formula (II-1) or (II-4) shown below isparticularly desirable.

In the formulas, each R² independently represents an organic group whichmay have a fluorine atom.

In general formulas (II-1) to (II-4), R² represents an organic groupwhich may have a fluorine atom. An “organic group” is a group containingat least one carbon atom.

The structure of R² may be linear, branched or cyclic, and is preferablylinear or branched.

In R², the organic group preferably has 1 to 20 carbon atoms, morepreferably 1 to 15 carbon atoms, still more preferably 1 to 10 carbonatoms, and most preferably 1 to 5 carbon atoms.

The fluorination ratio within R² is preferably 25% or more, morepreferably 50% or more, and most preferably 60% or more, as thehydrophobicity of the resist film during immersion exposure is enhanced.The term “fluorination ratio” refers to the percentage (%) of the numberof fluorine atoms based on the total number of hydrogen atoms andfluorine atoms contained within the organic group.

As a preferable example of R², a fluorinated hydrocarbon group which mayor may not have a substituent can be given.

The hydrocarbon group may be either an aliphatic hydrocarbon group or anaromatic hydrocarbon group, and an aliphatic hydrocarbon group ispreferable.

An aliphatic hydrocarbon group refers to a hydrocarbon group having noaromaticity. The aliphatic hydrocarbon group may be either saturated orunsaturated, but in general, the aliphatic hydrocarbon group ispreferably saturated.

As R², a fluorinated, saturated hydrocarbon group or a fluorinated,unsaturated hydrocarbon group is preferable, more preferably afluorinated, saturated hydrocarbon group, and most preferably afluorinated alkyl group.

Examples of fluorinated alkyl groups include groups in which part or allof the hydrogen atoms within the below described unsubstituted alkylgroups have been substituted with a fluorine atom. The fluorinated alkylgroup may be either a group in which part of the hydrogen atoms withinan unsubstituted alkyl group described below has been substituted with afluorine atom, or a group in which all of the hydrogen atoms within anunsubstituted alkyl group described below has been substituted with afluorine atom (i.e., a perfluoroalkyl group).

The unsubstituted alkyl group may be linear, branched or cyclic.Alternatively, the unsubstituted alkyl group may be a combination of alinear or branched alkyl group with a cyclic alkyl group.

The unsubstituted linear alkyl group preferably has 1 to 10 carbonatoms, and more preferably 1 to 8. Specific examples include a methylgroup, an ethyl group, an n-propyl group, an n-butyl group, an n-pentylgroup, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonylgroup and an n-decyl group.

The unsubstituted branched alkyl group preferably has 3 to 10 carbonatoms, and more preferably 3 to 8. As the branched alkyl group, atertiary alkyl group is preferable.

As an example of an unsubstituted cyclic alkyl group, a group in whichone hydrogen atom has been removed from a monocycloalkane or apolycycloalkane such as a bicycloalkane, tricycloalkane ortetracycloalkane can be given. Specific examples include monocycloalkylgroups such as a cyclopentyl group and a cyclohexyl group; andpolycycloalkyl groups such as an adamantyl group, a norbornyl group, anisobornyl group, a tricyclodecyl group and a tetracyclododecyl group.

Examples of the combination of a linear or branched alkyl group with acyclic alkyl group include groups in which a cyclic alkyl group as asubstituent is bonded to a linear or branched alkyl group, and groups inwhich a linear or branched alkyl group as a substituent is bonded to acyclic alkyl group.

Examples of substituents for the fluorinated hydrocarbon group includean alkyl group of 1 to 5 carbon atoms.

As the fluorinated alkyl group for R², a linear or branched fluorinatedalkyl group is preferable. In particular, a group represented by generalformula (III-1) or (III-2) shown below is desirable, and a grouprepresented by general formula (III-1) is most preferable.

In general formula (III-1), R⁴¹′, represents an unsubstituted alkylenegroup of 1 to 9 carbon atoms, and R⁴²′ represents a fluorinated alkylgroup of 1 to 9 carbon atoms, provided that the total number of carbonatoms of R⁴¹′ and R⁴²′ is no more than 10. In general formula (III-2),each of R⁷¹ to R⁷³ independently represents a linear alkyl group of 1 to5 carbon atoms, with the provision that at least one of R⁷¹ to R⁷³represents an alkyl group having a fluorine atom.

In general formula (III-1), the alkylene group for R⁴¹′ may be linear,branched or cyclic, and is preferably linear or branched. Further, thenumber of carbon atoms within the alkylene group is preferably within arange of from 1 to 5.

As R⁴¹′, a methylene group, an ethylene group or a propylene group isparticularly desirable.

As R⁴²′, a linear or branched fluorinated alkyl group of 1 to 5 carbonatoms is preferable, and a perfluoroalkyl group is particularlydesirable. Among perfluoroalkyl groups, a trifluoromethyl group and atetrafluoroethyl group is preferable.

In general formula (III-2), as the alkyl group for R⁷¹ to R⁷³, an ethylgroup or a methyl group is preferable, and a methyl group isparticularly desirable. At least one of the alkyl groups for R⁷¹ to R⁷³is a fluorinated alkyl group, and all of the alkyl groups for R⁷¹ to R⁷³may be fluorinated alkyl groups.

As a preferable example of the structural unit (f1), a structural unitrepresented by general formula (f1-1) shown below can be given.

In the formula, R represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; X⁰⁰represents a divalent linking group which may have a substituent; and R²represents an organic group which may have a fluorine atom; providedthat at least one of X⁰⁰ and R² has a fluorine atom.

In general formula (f1-1), R represents a hydrogen atom, an alkyl groupof 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbonatoms, and is the same as defined for R described above in theexplanation of the component (A).

Specific examples of the alkyl group of 1 to 5 carbon atoms for Rinclude linear or branched alkyl groups of 1 to 5 carbon atoms such as amethyl group, an ethyl group, a propyl group, an isopropyl group, ann-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, anisopentyl group and a neopentyl group.

Specific examples of the halogenated alkyl group of 1 to 5 carbon atomsrepresented by R include groups in which part or all of the hydrogenatoms of the aforementioned alkyl groups of 1 to 5 carbon atoms havebeen substituted with halogen atoms. Examples of the halogen atominclude a fluorine atom, a chlorine atom, a bromine atom and an iodineatom, and a fluorine atom is particularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, a hydrogenatom or a methyl group is more preferable, and a methyl group isparticularly desirable.

In general formula (f1-1), X⁰⁰ represents a divalent linking group whichmay have a substituent.

With respect to the divalent linking group represented by X⁰⁰, thedivalent linking group may “have a substituent” means that part or allof the hydrogen atoms of the linking group may be substituted withgroups or atoms other than hydrogen atoms.

The divalent linking group for X⁰⁰ may or may not have an aciddissociable portion in the structure thereof.

An “acid dissociable portion” refers to a portion within the X⁰⁰ groupwhich is dissociated from the group by action of acid generated from thecomponent (B) upon exposure. Specific examples of such acid dissociableportion include a portion that forms a cyclic or chain-like tertiaryalkyl ester with the carbonyl group; and a portion in which one or morehydrogen atoms have been removed from a group bonded to the oxygen atomconstituting the acetal structure of an acetal-type acid dissociable,dissolution inhibiting group such as an alkoxyalkyl group.

As preferable examples of the divalent linking group for X⁰⁰, a divalenthydrocarbon group which may have a substituent, and a divalent linkinggroup containing a hetero atom can be given.

As examples of the divalent hydrocarbon group which may have asubstituent and the divalent linking group containing a hetero atom, thesame groups as those described above for the “divalent hydrocarbon groupwhich may have a substituent” and the “divalent linking group containinga hetero atom” in relation to R⁰² in general formula (a0-1) can begiven.

The divalent linking group for X⁰⁰ may be the “divalent hydrocarbongroup which may have a substituent” or the “divalent linking groupcontaining a hetero atom” which may or may not have a fluorine atom.

In the present invention, the divalent linking group for X⁰⁰ ispreferably a linear or branched alkylene group, a divalent linking groupcontaining a divalent aromatic cyclic group or a hetero atom, or any ofthese groups containing a fluorine atom. Among these, a divalent linkinggroup containing a hetero atom which may have a fluorine atom isparticularly desirable.

When X⁰⁰ represents a linear or branched alkylene group, it preferablyhas 1 to 10 carbon atoms, more preferably 1 to 6, still more preferably1 to 4, and most preferably 1 to 3. Specific examples include the samelinear alkylene groups and branched alkylene groups as those describedabove for the “divalent hydrocarbon group which may have a substituent”.

When X⁰⁰ represents a divalent aromatic cyclic group, examples of thearomatic cyclic group include a divalent aromatic hydrocarbon group inwhich one hydrogen atom has been removed from the nucleus of amonovalent aromatic hydrocarbon group such as a phenyl group, a biphenylgroup, a fluorenyl group, a naphthyl group, an anthryl group or aphenanthryl group; an aromatic hydrocarbon group in which part of thecarbon atoms constituting the ring of the aforementioned divalentaromatic hydrocarbon group has been substituted with a hetero atom suchas an oxygen atom, a sulfur atom or a nitrogen atom; and an aromatichydrocarbon group in which one hydrogen atom has been removed from abenzene ring of an arylalkyl group such as a benzyl group, a phenethylgroup, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a1-naphthylethyl group or a 2-naphthylethyl group.

When X⁰⁰ represents a divalent linking group containing a hetero atom,preferable examples of the divalent linking group include —O—,—C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NR⁰⁴—(R⁰⁴ represents asubstituent such as an alkyl group or an acyl group), —S—, —S(═O)₂—,—S(═O)₂—O—, a group represented by the formula —C(═O)—O—R⁰⁸—, a grouprepresented by the formula —O—R⁰⁸—, a group represented by the formula—R⁰⁹—O— and a group represented by the formula —R⁰⁹—O—R⁰⁸—.

R⁰⁸ represents a divalent hydrocarbon group which may have asubstituent, preferably a linear or branched aliphatic hydrocarbongroup, and more preferably an alkylene group or an alkylalkylene group.

As the alkylene group, a methylene group or an ethylene group isparticularly desirable.

The alkyl group within the alkylalkylene group is preferably a linearalkyl group of 1 to 5 carbon atoms, more preferably a linear alkyl groupof 1 to 3 carbon atoms, and most preferably an ethyl group.

The R⁰⁸ groups may or may not contain a fluorine atom.

R⁰⁹ represents a divalent aromatic cyclic group, preferably a group inwhich one hydrogen atom has been removed from the nucleus of amonovalent aromatic hydrocarbon group, and most preferably a group inwhich one hydrogen atom has been removed from a naphthyl group.

In general formula (f1-1), R² represents an organic group which may havea fluorine atom, and is the same as defined for R² in general formulas(II-1) to (II-4).

Among the aforementioned examples, when the structural unit (f1) isrepresented by general formula (f1-1) in which X⁰⁰ is a single bond, R²is preferably a methyl group or an ethyl group.

On the other hand, when the structural unit (f1) is represented bygeneral formula (f1-1) in which X⁰⁰ is a divalent linking group whichmay have a fluorine atom, it is preferably a structural unit representedby general formula (f1-1-1) shown below or general formula (f1-1-2)described later.

In the formulas, each R independently represents a hydrogen atom, analkyl group of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to5 carbon atoms; X represents a divalent linking group which may have asubstituent; A_(aryl) represents a divalent aromatic group which mayhave a substituent; X⁰¹ represents a single bond or a divalent linkinggroup which may have a substituent; and R² represents an organic groupwhich may have a fluorine atom; provided that in general formula(f1-1-1), at least one of X and R² has a fluorine atom, and in generalformula (f1-1-2), at least one of X⁰¹ and R² has a fluorine atom.

In general formulas (f1-1-1) and (f1-1-2), as the alkyl group of 1 to 5carbon atoms represented by R, a linear or branched lower alkyl group ispreferable, and specific examples thereof include a methyl group, anethyl group, a propyl group, an isopropyl group, an n-butyl group, anisobutyl group, a tert-butyl group, a pentyl group, an isopentyl groupand a neopentyl group.

Specific examples of the halogenated alkyl group of 1 to 5 carbon atomsinclude groups in which part or all of the hydrogen atoms of theaforementioned “alkyl group of 1 to 5 carbon atoms” have beensubstituted with a halogen atom. Examples of the halogen atom include afluorine atom, a chlorine atom, a bromine atom and an iodine atom, and afluorine atom is particularly desirable.

As R, a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or afluorinated alkyl group of 1 to 5 carbon atoms is preferable, and ahydrogen atom or a methyl group is more preferable in terms ofindustrial availability.

In formulas (f1-1-1) and (f1-1-2), R² is the same as defined above. Ingeneral formula (f1-1-1), when X has no fluorine atom, as R², afluorinated hydrocarbon group is preferable, a fluorinated alkyl groupis more preferable, a fluorinated alkyl group of 1 to 5 carbon atoms isstill more preferable, and —CH₂—CF₃, —CH₂—CF₂-CF₃, —CH(CF₃)₂,—CH₂—CF₂—CF₂—CF₃, and —CH₂—CH₂—CF₂—CF₂—CF₂—CF₃ are most preferable.

In general formula (f1-1-1), when X has a fluorine atom, in addition tothose described above, an alkyl group of 1 to 5 carbon atoms ispreferable, and a methyl group is particularly desirable.

In general formula (f-1-2), R² is the same as defined above. In generalformula (f1-2), as R², a fluorinated hydrocarbon group is preferable, afluorinated alkyl group is more preferable, a fluorinated alkyl group of1 to 5 carbon atoms is still more preferable, and —CH₂—CF₃,—CH₂—CF₂—CF₃, —CH(CF₃)₂, —CH₂—CF₂—CF₂—CF₃, and —CH₂—CH₂—CF₂—CF₂—CF₂—CF₃are most preferable.

In general formula (f1-1-1), X represents a divalent linking group whichmay have a substituent.

X may or may not have an acid dissociable portion. An “acid dissociableportion” refers to a portion within the organic group which isdissociated from the organic group by the action of acid generated uponexposure. When X has an acid dissociable portion, it is preferable thatthe acid dissociable portion has a tertiary carbon atom.

Preferable examples of X include a hydrocarbon group which may have asubstituent, and a group containing a hetero atom.

A hydrocarbon “has a substituent” means that part or all of the hydrogenatoms within the hydrocarbon group is substituted with groups or atomsother than hydrogen.

The hydrocarbon group may be either an aliphatic hydrocarbon group or anaromatic hydrocarbon group. An “aliphatic hydrocarbon group” refers to ahydrocarbon group that has no aromaticity.

The aliphatic hydrocarbon group may be either saturated or unsaturated,but in general, the aliphatic hydrocarbon group is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear orbranched aliphatic hydrocarbon group, and an aliphatic hydrocarbon groupcontaining a ring in the structure thereof can be given.

The linear or branched aliphatic hydrocarbon group preferably has 1 to10 carbon atoms, more preferably 1 to 8, still more preferably 1 to 5,and most preferably 1 or 2.

As the linear aliphatic hydrocarbon group, a linear alkylene group ispreferable.

Specific examples thereof include a methylene group [—CH₂—], an ethylenegroup [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], a tetramethylenegroup [—(CH₂)₄—] and a pentamethylene group [—(CH₂)₅—].

As the branched aliphatic hydrocarbon group, branched alkylene groupsare preferred, and specific examples include various alkylalkylenegroups, including alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—,—C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—;alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—,—C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylenegroups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; andalkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and—CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, alinear alkyl group of 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group (chain-like aliphatichydrocarbon group) may or may not have a substituent. Examples of thesubstituent include a fluorine atom, a fluorinated alkyl group of 1 to 5carbon atoms, and an oxygen atom (═O). Among these, a chain-likealiphatic hydrocarbon group containing a fluorine atom is preferable. Ingeneral formula (f1-1-1), at least one of X and R² has a fluorine atom.

As examples of the hydrocarbon group containing a ring, a cyclicaliphatic hydrocarbon group (a group in which two hydrogen atoms havebeen removed from an aliphatic hydrocarbon ring), and a group in whichthe cyclic aliphatic hydrocarbon group is bonded to the terminal of theaforementioned chain-like aliphatic hydrocarbon group or interposedwithin the aforementioned chain-like aliphatic hydrocarbon group, can begiven.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbonatoms, and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic groupor a monocyclic group. As the monocyclic group, a group in which twohydrogen atoms have been removed from a monocycloalkane of 3 to 6 carbonatoms is preferable. Examples of the monocycloalkane includecyclopentane and cyclohexane. As the polycyclic group, a group in whichtwo hydrogen atoms have been removed from a polycycloalkane of 7 to 12carbon atoms is preferable. Examples of the polycycloalkane includeadamantane, norbornane, isobornane, tricyclodecane andtetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include an alkyl group of 1 to5 carbon atoms, a fluorine atom, a fluorinated alkyl group of 1 to 5carbon atoms, and an oxygen atom (═O).

With respect to a divalent group containing a hetero atom, a hetero atomis an atom other than carbon and hydrogen, and examples thereof includean oxygen atom, a nitrogen atom, a sulfur atom and a halogen atom.

Specific examples of divalent groups containing a hetero atom include—O—, —C(═O)—, —C(═O)—O—, a carbonate bond (—O—C(═O)—O—), —NH—, —NR⁰⁰⁴(in the formula, R⁰⁰⁴ represents an alkyl group), —NH—C(═O)—, ═N—, and acombination of any of these “groups” with a divalent hydrocarbon group.As examples of the divalent hydrocarbon group, the same groups as thosedescribed above for the hydrocarbon group which may have a substituentcan be given, and a linear or branched aliphatic hydrocarbon group ispreferable.

In general formula (f1-1-2), A_(aryl) represents a divalent aromaticcyclic group which may have a substituent. A specific example ofA_(aryl) includes an aromatic hydrocarbon ring (which may have asubstituent) having two hydrogen atoms removed therefrom.

The ring skeleton of the aromatic cyclic group for A_(aryl) preferablyhas 6 to 15 carbon atoms. Examples of the ring skeleton include abenzene ring, a naphthalene ring, a phenanthrene ring and an anthracenering. Among these, a benzene ring or a naphthalene ring is particularlydesirable.

Examples of substituents for the aromatic cyclic group represented byA_(aryl) include a halogen atom, an alkyl group, an alkoxy group, ahalogenated alkyl group of 1 to 5 carbon atoms, and an oxygen atom (═O).Examples of the halogen atom include a fluorine atom, a chlorine atom,an iodine atom and a bromine atom. As the substituent for the aromaticcyclic group represented by A_(aryl), a fluorine atom is preferable.

A_(aryl) may be either an aromatic cyclic group having no substituent,or an aromatic cyclic group having a substituent, although an aromaticcyclic group having no substituent is preferable.

When A_(aryl) represents an aromatic cyclic group having a substituent,the number of the substituent may be 1 or more, preferably 1 or 2, andmore preferably 1.

X⁰¹ represents a single bond or a divalent linking group which may havea substituent. Examples of divalent linking groups include an alkylenegroup of 1 to 10 carbon atoms, —O—, —C(═O)—, —C(═O)—O—, a carbonate bond(—O—C(═O)—O—), —NH—C(═O)—, and a combination of these groups. Of these,a combination of —O— with an alkylene group of 1 to 10 carbon atoms isparticularly desirable. Examples of the substituent include a fluorineatom, a fluorinated alkyl group of 1 to 5 carbon atoms, and an oxygenatom (═O). Among these, a substituent group containing a fluorine atomis preferable. In general formula (f1-1-2), at least one of X⁰¹ and R²has a fluorine atom.

Examples of alkylene groups of 1 to 10 carbon atoms include linear,branched or cyclic alkylene groups, and a linear or branched alkylenegroup of 1 to 5 carbon atoms and a cyclic alkylene group of 4 to 10carbon atoms are preferable.

Among structural units represented by the aforementioned general formula(f1-1-1), structural units represented by general formulas (f1-01-11) to(f1-01-17) shown below are preferable.

Further, among structural units represented by the aforementionedgeneral formula (f1-1-2), structural units represented by generalformulas (f1-01-21) to (f1-01-26) shown below are preferable.

In general formulas (f1-01-11) to (f1-01-17) and (f1-01-21) to(f1-01-26), R and R² are the same as defined above; each of R⁵⁶ and R⁵⁷independently represents an alkyl group of 1 to 12 carbon atoms; each ofR⁵⁸ and R⁵⁹ independently represents a hydrogen atom or an alkyl groupof 1 to 12 carbon atoms; each of a1, a2, a3, a5, a7 a9 and a11 to a13independently represents an integer of 1 to 5; each of a4, a6, a8 anda10 independently represents an integer of 0 to 5; each of a14 to a16independently represents an integer of 1 to 5; each of d1 to d5independently represents 0 or 1; R^(q5) represents a substituent; erepresents an integer of 0 to 2; and A₁ represents a cyclic alkylenegroup of 4 to 20 carbon atoms.

In formulas (f1-01-11) to (f1-01-17) and (f1-01-21) to (f1-01-26), as R,a hydrogen atom or a methyl group is preferable.

In general formula (f1-01-11), a1 is preferably an integer of 1 to 3,more preferably 1 or 2.

In formula (f1-01-12), it is preferable that each of a2 and a3independently represent an integer of 1 to 3, and more preferably 1 or2.

d1 is preferably 0.

In formula (f1-01-13), a4 is preferably an integer of 0 to 3, morepreferably an integer of 0 to 2, and most preferably 0 or 1.

a5 is preferably an integer of 1 to 3, and more preferably 1 or 2.

Examples of the substituent represented by R^(q5) include a halogenatom, an alkyl group of 1 to 5 carbon atoms, an alkoxy group of 1 to 5carbon atoms, a halogenated alkyl group of 1 to 5 carbon atoms and anoxygen atom (═O). Examples of the alkyl group of 1 to 5 carbon atomsinclude the same alkyl group of 1 to 5 carbon atoms as those describedabove for R. Examples of the halogen atom include a fluorine atom, achlorine atom, an iodine atom and a bromine atom. Examples of thehalogenated alkyl group of 1 to 5 carbon atoms include the samehalogenated alkyl group of 1 to 5 carbon atoms as those described abovefor R.

e is preferably 0 or 1, and most preferably 0 from an industrialviewpoint.

d2 is preferably 0.

In general formula (f1-01-14), a6 is preferably an integer of 0 to 3,more preferably an integer of 0 to 2, and most preferably 0 or 1.

a7 is preferably an integer of 1 to 3, and more preferably 1 or 2.

d3 is preferably 0.

R^(q5) and e are the same as defined above.

In formula (f1-01-15), a14 is preferably an integer of 0 to 3, morepreferably an integer of 0 to 2, and most preferably 0 or 1.

It is preferable that each of R⁵⁶ and R⁵⁷ independently represents alinear, branched or cyclic alkyl group of 1 to 12 carbon atoms, andspecific examples thereof include a methyl group, an ethyl group, ann-propyl group, an isopropyl group, an n-butyl group, an isobutyl group,a tert-butyl group, a tert-pentyl group, a cyclopentyl group, acyclohexyl group, a cyclooctyl group, a norbornyl group, an isobornylgroup, a tricyclodecyl group, an adamantyl group and a tetracyclododecylgroup. Of these, an alkyl group of 1 to 6 carbon atoms is preferable,more preferably an alkyl group of 1 to 4 carbon atoms, and mostpreferably a methyl group or an ethyl group.

It is preferable that each of R⁵⁸ and R⁵⁹ independently represents ahydrogen atom, or a linear, branched or cyclic alkyl group of 1 to 12carbon atoms. For R⁵⁸ and R⁵⁹, the linear, branched or cyclic alkylgroup of 1 to 12 carbon atoms is the same as defined above for R⁵⁶ andR⁵⁷.

In formula (f1-01-16), A₁ represents a cyclic alkylene group of 4 to 20carbon atoms, and is preferably a cyclic alkylene group of 5 to 15carbon atoms, and more preferably a cyclic alkylene group of 6 to 12carbon atoms. Specific examples of the cyclic alkylene group includethose described above as the “cyclic aliphatic hydrocarbon group” forthe aforementioned hydrocarbon group which may have a substituent, andthe cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbonatoms, and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic groupor a monocyclic group. As the monocyclic group, a group in which twohydrogen atoms have been removed from a monocycloalkane of 3 to 6 carbonatoms is preferable. Examples of the monocycloalkane includecyclopentane and cyclohexane.

As the polycyclic group, a group in which two hydrogen atoms have beenremoved from a polycycloalkane of 7 to 12 carbon atoms is preferable.Examples of the polycycloalkane include adamantane, norbornane,isobornane, tricyclodecane and tetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have asubstituent. Examples of the substituent include an alkyl group of 1 to5 carbon atoms, a fluorine atom, a fluorinated alkyl group of 1 to 5carbon atoms, and an oxygen atom (═O).

In general formula (f1-01-17), R^(q1) represents a fluorine atom or afluorinated alkyl group.

With respect to the fluorinated alkyl group for R^(q1), the alkyl groupprior to being fluorinated may be linear, branched or cyclic.

The linear or branched alkyl group preferably has 1 to 5 carbon atoms,more preferably 1 to 3 carbon atoms, and most preferably 1 or 2 carbonatoms.

In general formula (f1-0′-17), each of R^(q3) and R^(q4) independentlyrepresents a hydrogen atom, an alkyl group or a fluorinated alkyl group,wherein R^(q) and R^(q4) may be mutually bonded to form a ring.

The alkyl group for R^(q3) and R^(q4) may be linear, branched or cyclic,and is preferably linear or branched.

The linear or branched alkyl group is preferably a linear or branchedalkyl group of 1 to 5 carbon atoms, more preferably a methyl group or anethyl group, and most preferably an ethyl group.

The cyclic alkyl group preferably has 4 to 15 carbon atoms, morepreferably 4 to 12, and most preferably 5 to 10. Specific examplesinclude groups in which one or more hydrogen atoms have been removedfrom a monocycloalkane or a polycycloalkane such as a bicycloalkane,tricycloalkane or tetracycloalkane. Specific examples include groups inwhich one or more hydrogen atoms have been removed from amonocycloalkane such as cyclopentane and cyclohexane; and groups inwhich one or more hydrogen atoms have been removed from apolycycloalkane such as adamantane, norbornane, isobornane,tricyclodecane or tetracyclododecane. Among these examples, a group inwhich one or more hydrogen atoms have been removed from adamantane ispreferable.

The fluorinated alkyl group for R^(q3) and R^(q4) is an alkyl group inwhich part or all of the hydrogen atoms have been substituted with afluorine atom.

In the fluorinated alkyl group, the alkyl group prior to beingsubstituted with a fluorine atom may be linear, branched or cyclic, andexamples thereof include the same groups as those described above forthe alkyl group represented by R^(q3) and R^(q4).

R^(q3) and R^(q4) may be mutually bonded to form a ring. Such a ringconstituted of R^(q3), R^(q4) and the carbon atom having R^(q3) andR^(q4) bonded thereto can be mentioned as a group in which two hydrogenatoms have been removed from a monocycloalkane or a polycycloalkanedescribed above for the aforementioned cyclic alkyl group, preferably a4- to 10-membered ring, and more preferably a 5- to 7-membered ring.

Among these, R^(q3) and R^(q4) preferably represents a hydrogen atom oran alkyl group.

In formula (f1-01-21), a8 is preferably an integer of 0 to 3, morepreferably an integer of 0 to 2, and most preferably 0 or 1.

a9 is preferably an integer of 1 to 3, and more preferably 1 or 2.

d4 is preferably 0.

R⁵ and e are the same as defined above.

In formula (f1-01-22), a10 is preferably an integer of 0 to 3, morepreferably an integer of 0 to 2, and most preferably 0 or 1.

a11 is preferably an integer of 1 to 3, and more preferably 1 or 2.

d5 is preferably 0.

R^(q5) and e are the same as defined above.

In formula (f1-01-23), a12 is preferably an integer of 1 to 3, and morepreferably 1 or 2.

R^(q5) and e are the same as defined above.

In formula (f1-01-24), a13 is preferably an integer of 1 to 3, and morepreferably 1 or 2.

R^(q5) and e are the same as defined above.

In formulas (f1-01-25) and (f1-01-26), each of a15 and a16 is preferablyan integer of 0 to 3, more preferably an integer of 0 to 2, and mostpreferably 0 or 1.

R⁵⁶, R⁵⁷, R⁵⁸ and R⁵⁹ are the same as defined above.

In general formulas (f1-01-25) and (f1-01-26), R^(q5) and e are the sameas defined above.

Specific examples of structural units represented by the above generalformulas (f1-01-11) to (f1-01-17) and (f1-01-21) to (f1-01-26) are shownbelow.

As the structural unit (f1-1), at least one structural unit selectedfrom the group consisting of structural units represented by theaforementioned general formulas (f1-01-11) to (f1-01-17) and (f1-01-21)to (f1-01-26) is preferable, at least one structural unit selected fromthe group consisting of structural units represented by theaforementioned general formulas (f1-01-11) to (f1-01-17) and (f1-01-21)to (f1-01-24) is more preferable, at least one structural unit selectedfrom the group consisting of structural units represented by theaforementioned general formulas (f1-01-11) to (f1-01-17), (f1-01-21) and(f1-01-22) is still more preferable, and at least one structural unitselected from the group consisting of structural units represented bythe aforementioned general formulas (f1-01-11), (f1-01-17) and(f1-01-22) is most preferable.

Examples of the monomers from which the structural unit represented bygeneral formula (f1-1) is derived include compounds in which an alkalideveloping solution decomposable group and a polymerizable group arebonded via a divalent linking group.

A “polymerizable group” refers to a group that renders a compound havingthe group polymerizable by a radical polymerization or the like, andexamples of the polymerizable groups include groups containing anethylenic double bond. Examples of the groups containing an ethylenicdouble bond include a group represented by CH₂═CR— (in the formula, R isthe same as defined above).

Examples of the divalent linking groups include a group represented bythe formula -A_(aryl)-X₀₁- (in the formula, A_(aryl) and X₀₁ are thesame as defined above) and a group represented by the formula—C(═O)—O—X— (in the formula, X is the same as defined above).

Examples of the monomers from which the structural unit represented bygeneral formula (f1-1-1) is derived include a fluorine-containingcompound represented by general formula (f1-01-10) shown below, andexamples of the monomers from which the structural unit represented bygeneral formula (f1-1-2) is derived include a fluorine-containingcompound represented by general formula (f1-01-20) shown below.

In the formulas, R, X, A_(aryl), X₀₁ and R¹ are the same as definedabove.

A fluorine-containing compound represented by general formula (f1-01-10)or (f1-01-20) (hereafter, frequently referred to as “fluorine-containingcompound (F0)”) can be produced, for example, by introducing the R¹group (R¹ is the same as defined above) into the carboxy group of acompound represented by general formula (f0-1-0) or (f0-2-0) shown below(hereafter, collectively referred to as “compound (V-1)”) (i.e.,substituting the hydrogen atom at the terminal of the carboxy group withthe R¹ group).

The R¹ group can be introduced by a conventional method. For example, acompound (V-1) can be reacted with a compound (V-2) represented bygeneral formula (V-2) shown below, to thereby obtain afluorine-containing compound (F0).

In the formulas, R, X, A_(aryl), X₀₁ and R¹ are the same as definedabove.

The method of reacting a compound (V-1) with a compound (V-2) is notparticularly limited. For example, a method in which a compound (V-1)comes in contact with a compound (V-2) in a reaction solvent in thepresence of a base can be used.

As a compound (V-1) and a compound (V-2), commercially availablecompounds can be used. Alternatively, a compound (V-1) and a compound(V-2) can be synthesized.

As a compound (V-1), for example, a low molecular weight compoundderived from an acrylate ester such as a carboxyalkyl (meth)acrylate ora mono((meth)acryloyloxyalkyl)succinate, or a polymeric compoundincluding a structural unit derived from an acrylate ester can be used.

As a compound (V-2), for example, a fluorinated alkylalcohol or the likecan be used.

As the reaction solvent, any solvent capable of dissolving a compound(V-1) and a compound (V-2) (which are raw materials) can be used.Specific examples include tetrahydrofuran (THF), acetone,dimethylformamide (DMF), dimethylacetamide, dimethylsulfoxide (DMSO) andacetonitrile.

Examples of the base include organic bases such as triethylamine,4-dimethylaminopyridine (DMAP) and pyridine; and inorganic bases such assodium hydride, K₂CO₃ and Cs₂CO₃.

Examples of condensing agents include carbodiimide reagents such asethyldiisopropylaminocarbodiimide hydrochloride (EDCI),dicyclohexylcarboxylmide (DCC), diisopropylcarbodiimide andcarbodiimidazole; tetraethyl pyrophosphate; andbenzotriazole-N-hydroxytrisdimethylaminophosphonium hexafluorophosphide(Bop reagent).

If desired, an acid may be used. As the acid, any acid generally usedfor dehydration/condensation may be used. Specific examples includeinorganic acids such as hydrochloric acid, sulfuric acid and phosphoricacid; and organic acids such as methanesulfonic acid,trifluoromethanesulfonic acid, benzenesulfonic acid andp-toluenesulfonic acid. These acids can be used individually, or in acombination of two or more.

The amount of the compound (V-2) added, relative to the compound (V-1)is preferably within a range from 1 to 3 equivalents, and morepreferably from 1 to 2 equivalents.

The reaction temperature is preferably −20 to 40° C., more preferably 0to 30° C.

The reaction time varies depending on factors such as the reactivity ofthe compound (V-1) and the compound (V-2) and the reaction temperature.However, in general, the reaction time is preferably within a range from30 to 480 minutes, and more preferably from 60 to 360 minutes.

In the component (F1), the amount of the structural unit (f1), based onthe combined total of all structural units constituting the component(F1) is preferably 10 to 95 mol %, more preferably 30 to 80 mol %, andstill more preferably 40 to 70 mol %.

When the amount of the structural unit represented by general formula(f1-01) is at least as large as the lower limit of the above-mentionedrange, a high hydrophobicity can be achieved during formation of aresist pattern, and a resist film exhibiting excellent lithographyproperties can be obtained.

In the component (F1), as the structural unit (f1), one type ofstructural unit may be used, or two or more types may be used incombination.

In the component (F), the fluorine-containing polymeric compound (F1)may include a structural unit other than the structural unit (f1)(hereafter, referred to as “structural unit (f2)” or “structural unit(f3)”), as long as the effects of the present invention are notimpaired.

(Structural Unit (f2))

Examples of the structural unit (f2) include the structural units (a0)to (a4) described above in relation to the resin component (A1), and thestructural unit (a1) is preferable.

In the component (F1), as the structural unit (f2), one type ofstructural unit may be used, or two or more types may be used incombination.

Of the various structural units classified as the structural unit (a1),structural units represented by general formula (a1-0-11), (a1-0-12) or(a1-0-2) is preferable, and structural units represented by generalformulas (a1-1-16) to (a1-1-23), (a1-1-32) and (a1-1-33) areparticularly desirable.

In the component (F), as the structural unit (f2), one type ofstructural unit may be used alone, or two or more types of structuralunits may be used in combination.

In the component (F), the amount of the structural unit (f2) based onthe combined total of all structural units constituting the component(F) is preferably 5 to 80 mol %, more preferably 10 to 60 mol %, stillmore preferably 15 to 50 mol %, and most preferably 20 to 40 mol %. Whenthe amount of the structural unit (f2) is at least as large as the lowerlimit of the above-mentioned range, the characteristic feature ofexhibiting hydrophobicity during immersion exposure, but then exhibitingincreased hydrophilicity during exposure and post exposure baking (PEB)is improved. Moreover, formation of bridge-type defects in a line andspace pattern or formation of “Not Open” defects in which a portion of,or all of, a contact hole pattern is not open can be suppressed.Furthermore, the proportion of hydrocarbon groups within the component(F) increases and the water tracking ability during immersion exposureusing a scanning-type immersion exposure apparatus is improved. On theother hand, when the amount of the structural unit (f2) is no more thanthe upper limit of the above-mentioned range, a good balance can beachieved with the structural unit (f1), and the effects of the presentinvention are improved.

(Structural Unit (f3))

There are no particular limitations on the structural unit (f3),provided the structural unit is derived from a compound that iscopolymerizable with the compound from which the structural unit (f1) isderived and the compound from which the structural unit (f2) is derived.Examples of such structural units include structural units which havebeen proposed for the base resin of a conventional chemically amplifiedresist. Among these, a structural unit that contains an alkali-solublegroup such as a carboxy group or a hydroxy group in the structurethereof is particularly desirable.

As an example of the structural unit (f3), a structural unit representedby general formula (f3-1) shown below can be given.

In the formulas, R is the same as defined above.

In the component (F), as the structural unit (f3), one type ofstructural unit may be used alone, or two or more types of structuralunits may be used in combination. In the component (F), the amount ofthe structural unit (f3) based on the combined total of all structuralunits constituting the component (F) is preferably 5 to 80 mol %, morepreferably 10 to 60 mol %, still more preferably 15 to 50 mol %, andmost preferably 20 to 40 mol %.

In the present invention, the component (F) is preferably a copolymerincluding the structural unit (f1) and at least one of the structuralunit (f2) and the structural unit (f3). Examples of such copolymersinclude a copolymer consisting of the structural unit (f1) and thestructural unit (f2); a copolymer consisting of the structural unit (f1)and the structural unit (f3); and a copolymer consisting of thestructural unit (f1), the structural unit (f2) and the structural unit(f3).

The weight average molecular weight (Mw) (the polystyrene equivalentvalue determined by gel permeation chromatography) of the component (F)is not particularly limited, but is preferably 2,000 to 50,000, morepreferably 3,000 to 30,000, and most preferably 4,000 to 25,000. Whenthe weight average molecular weight is no more than the upper limit ofthe above-mentioned range, the resist composition exhibits asatisfactory solubility in a resist solvent. On the other hand, when theweight average molecular weight is at least as large as the lower limitof the above-mentioned range, dry etching resistance and thecross-sectional shape of the resist pattern becomes satisfactory.

Further, the dispersity (Mw/Mn) is preferably 1.0 to 5.0, morepreferably 1.0 to 3.0, and most preferably 1.2 to 2.5. Here, Mn is thenumber average molecular weight.

The component (F) can be produced, for example, by polymerization of themonomers corresponding with each of the structural units that constitutethe component (F) by a living radical polymerization using a livingradical polymerization initiator (e.g., azobisisobutyronitrile (AIBN) ordibutyl telluride) or any other conventional polymerization methodcapable of block copolymerization.

Polymerization of a block copolymer can be conducted by a conventionalmethod (see, for example, Japanese Unexamined Patent Application, FirstPublication No. 2004-323693, Japanese Unexamined Patent Application,First Publication No. 2005-126459, Japanese Unexamined PatentApplication, First Publication No. 2006-299278 and Japanese UnexaminedPatent Application, First Publication No. 2008-247919). For example, acompound from which a structural unit (f1) can be derived (hereafter,referred to as “compound (f1)”) can be reacted with compoundsrepresented by formulas (V-3), (V-4) and (V-5) shown below, to therebyobtain a fluorine-containing polymeric compound (F01).

In the formulas, R^(p1) represents an alkyl group of 1 to 8 carbonatoms, an aryl group, a substituted aryl group or an aromaticheterocyclic group; each of R^(p2) and R^(p3) independently represents ahydrogen atom or an alkyl group of 1 to 8 carbon atoms; R^(p4)represents an aryl group, a substituted aryl group, an aromaticheterocyclic group, an acyl group, an oxycarbonyl group or a cyanogroup; R^(p5) and R^(p6) represent an alkyl group of 1 to 10 carbonatoms, an alkyl group of 1 to 4 carbon atoms which has been substitutedwith a carboxy group, a phenyl group which may have a substituent,wherein R^(p5) and R^(p6) may be the same or different from each other,and R^(p5) and R^(p6) may form an aliphatic cyclic group together withthe carbon atom having the R^(p5) group and the R^(p6) group bondedthereto; and R^(p7) represents a cyano group, an acetoxy group, acarbamoyl group or an alkoxycarbonyl group in which the alkoxy group has1 to 4 carbon atoms.

The method of reacting a compound (f1) with a compound (V-3), a compound(V-4) and a compound (V-5) is not particularly limited. For example, thecompound (f1) can be allowed to come in contact with the compounds(V-3), (V-4) and (V-5) in an inert gas-purged vessel.

As a compound (V-3), a compound (V-4) and a compound (V-5), commerciallyavailable compounds can be used. Alternatively, the compounds can besynthesized.

As a compound (V-3), an organic tellurium compound may be used.

As a compound (V-4), a ditelluride compound may be used.

As a compound (V-5), an azo-type polymerization initiator may be used.

Although the reaction can be performed without a solvent, a reactionsolvent may be used. As the reaction solvent, any solvent which iscapable of dissolving the compounds as the raw materials can be used.Specific examples of such solvents include tetrahydrofuran (THF),acetone, dimethylformamide (DMF), dimethylacetamide, dimethylsulfoxide(DMSO) and dioxane.

The amount of the compound (f1) added, relative to the compounds (V-3)to (V-5) is preferably within a range from 5 to 10,000 equivalents, andmore preferably from 50 to 5,000 equivalents.

The amount of the compounds (V-3) to (V-5) is not particularly limited.The amount of the compound (V-4) relative to the compound (V-3) ispreferably 0.1 to 10 equivalents, and the amount of the compound (V-5)relative to the compound (V-3) is preferably 0.1 to 10 equivalents.

The reaction temperature is preferably within the range of 40 to 150°C., and more preferably 50 to 120° C.

The reaction time depends on the reactivity of the compounds, thereaction temperature or the like. However, in general, the reaction timeis preferably 0.5 to 96 hours, and more preferably 1 to 48 hours.

In the present invention, the component (F) contains afluorine-containing polymeric compound (F1) which has the structuralunit (f1).

Preferable examples of the fluorine-containing polymeric compound (F1)include a copolymer consisting of the structural unit (f1) and thestructural unit (f2), and a copolymer consisting of the structural unit(f1), the structural unit (f2) and the structural unit (f3).

In the present invention, as the component (F1), those which have thestructural units as shown below (fluorine-containing polymeric compounds(F1-1) to (F1-4)) are particularly desirable.

In formula (F1-1), R represents a hydrogen atom, an alkyl group of 1 to5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms,wherein the plurality of R may be the same or different from each other;j″ represents an integer of 1 to 3; R³⁰ represents an alkyl group of 1to 5 carbon atoms; and h″ represents an integer of 1 to 6.

In formula (F1-1), R is the same as defined for R in the aforementionedformulas (f1-1) to (f1-3).

j″ is preferably 1 or 2, and most preferably 1.

R³⁰ is the same as defined for the alkyl group of 1 to 5 carbon atomsrepresented by R, preferably a methyl group or an ethyl group, and anethyl group is particularly desirable.

h″ is preferably 3 or 4, and most preferably 4.

In formula (F1-2), R represents a hydrogen atom, an alkyl group of 1 to5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms,wherein the plurality of R may be the same or different from each other;each of R^(q2)′ and R^(q3)′ independently represents a hydrogen atom oran alkyl group; R² represents an alkyl group; R³⁰ represents an alkylgroup of 1 to 5 carbon atoms; and h″ represents an integer of 1 to 6.

In formula (F1-1), R is the same as defined for R in the aforementionedformula (F1-1).

R^(q2)′ and R^(q3)′ are respectively the same as defined for R^(q2)′ andR^(q3)′ in formula (F1-2).

R² is the same as defined above, preferably an alkyl group of 1 to 5carbon atoms, and more preferably a methyl group or an ethyl group.

R³⁰ and h″ are respectively the same as defined for R³⁰ and h″ informula (F1-1).

In formula (F1-3), R represents a hydrogen atom, an alkyl group of 1 to5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms,wherein the plurality of R may be the same or different from each other;j″ represents an integer of 1 to 3; R³⁰ represents an alkyl group of 1to 5 carbon atoms; and h″ represents an integer of 1 to 6.

In formula (F1-3), R is the same as defined for R in the aforementionedformulas (f1-1) to (f1-3).

j″ is preferably 1 or 2, and most preferably 1.

R³⁰ is the same as defined for the alkyl group of 1 to 5 carbon atomsrepresented by R, preferably a methyl group or an ethyl group, and anethyl group is particularly desirable.

h″ is preferably 3 or 4, and most preferably 4.

In formula (F1-4), R represents a hydrogen atom, an alkyl group of 1 to5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms,wherein the plurality of R may be the same or different from each other;j″ represents an integer of 1 to 3; R³⁰ represents an alkyl group of 1to 5 carbon atoms; h″ represents an integer of 1 to 6; each R′independently represents a hydrogen atom, an alkyl group of 1 to 5carbon atoms, an alkoxy group of 1 to 5 carbon atoms or —COOR″; R²⁹represents a single bond or a divalent linking group; and s″ representsan integer of 0 to 2.

In formula (F1-4), R is the same as defined for R in the aforementionedformulas (f1-1) to (f1-3).

j″ is preferably 1 or 2, and most preferably 1.

R³⁰ is the same as defined for the alkyl group of 1 to 5 carbon atomsrepresented by R, and a methyl group or an ethyl group is particularlydesirable.

In terms of industrial availability, R′ is preferably a hydrogen atom.

R²⁹ represents a single bond or a divalent linking group. Among these,an alkylene group, an ester bond (—C(═O)—O—) or a combination of theseis preferable. The alkylene group as a divalent linking group for R²⁹ ispreferably a linear or branched alkylene group.

s″ is preferably 1 or 2.

In the component (F), as the component (F1), one type may be used alone,or two or more types may be used in combination.

In the positive resist composition of the present invention, the amountof the component (F) relative to 100 parts by weight of the component(A) is preferably 0.1 to 50 parts by weight, more preferably 0.1 to 40parts by weight, still more preferably 0.3 to 30 parts by weight, andmost preferably 0.5 to 15 parts by weight. When the amount of thecomponent (F) is at least as large as the lower limit of theabove-mentioned range, the hydrophobicity of a resist film formed usingthe positive resist composition can be enhanced, so that the resist filmexhibits hydrophobicity suitable for immersion exposure. On the otherhand, when the amount of the component (F) is no more than the upperlimit of the above-mentioned range, the lithography properties areimproved.

The thus explained fluorine-containing resin component can also bepreferably used as an additive for a resist composition for immersionexposure.

<Component (D)>

In the positive resist composition of the present invention, anitrogen-containing organic compound (D) (hereafter referred to as thecomponent (D)) may be added as an optional component.

As the component (D), there is no particular limitation as long as itfunctions as an acid diffusion control agent, i.e., a quencher whichtraps the acid generated from the component (B) upon exposure. Amultitude of these components (D) have already been proposed, and any ofthese known compounds may be used, although an aliphatic amine, andparticularly a secondary aliphatic amine or tertiary aliphatic amine ispreferable. An aliphatic amine is an amine having one or more aliphaticgroups, and the aliphatic groups preferably have 1 to 12 carbon atoms.

Examples of these aliphatic amines include amines in which at least onehydrogen atom of ammonia (NH₃) has been substituted with an alkyl groupor hydroxyalkyl group of no more than 12 carbon atoms (i.e., alkylaminesor alkylalcoholamines), and cyclic amines.

Specific examples of alkylamines and alkylalcoholamines includemonoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine,n-nonylamine, and n-decylamine; dialkylamines such as diethylamine,di-n-propylamine, di-n-heptylamine, di-n-octylamine, anddicyclohexylamine; trialkylamines such as trimethylamine, triethylamine,tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine,tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine,tri-n-nonylamine, tri-n-decylamine, and tri-n-dodecylamine; and alkylalcohol amines such as diethanolamine, triethanolamine,diisopropanolamine, triisopropanolamine, di-n-octanolamine, andtri-n-octanolamine. Among these, trialkylamines of 5 to 10 carbon atomsare preferable, and tri-n-pentylamine is particularly desirable.

Examples of the cyclic amine include heterocyclic compounds containing anitrogen atom as a hetero atom. The heterocyclic compound may be amonocyclic compound (aliphatic monocyclic amine), or a polycycliccompound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine,and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, andspecific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene,1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and1,4-diazabicyclo[2.2.2]octane.

As the component (D), one type of compound may be used alone, or two ormore types may be used in combination.

In the present invention, as the component (D), it is preferable to usea trialkylamine of 5 to 10 carbon atoms.

The component (D) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A). When the amount of the component (D) is within theabove-mentioned range, the shape of the resist pattern and the postexposure stability of the latent image formed by the pattern-wiseexposure of the resist layer are improved.

<Optional Components>

[Component (E)]

Furthermore, in the positive resist composition of the presentinvention, for preventing any deterioration in sensitivity, andimproving the resist pattern shape and the post exposure stability ofthe latent image formed by the pattern-wise exposure of the resistlayer, at least one compound (E) (hereafter referred to as the component(E)) selected from the group consisting of an organic carboxylic acid,or a phosphorus oxo acid or derivative thereof can be added.

Examples of suitable organic carboxylic acids include acetic acid,malonic acid, citric acid, malic acid, succinic acid, benzoic acid, andsalicylic acid.

Examples of phosphorus oxo acids include phosphoric acid, phosphonicacid and phosphinic acid. Among these, phosphonic acid is particularlydesirable.

Examples of oxo acid derivatives include esters in which a hydrogen atomwithin the above-mentioned oxo acids is substituted with a hydrocarbongroup. Examples of the hydrocarbon group include an alkyl group of 1 to5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esterssuch as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esterssuch as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonicacid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid esterssuch as phenylphosphinic acid.

As the component (E), one type may be used alone, or two or more typesmay be used in combination.

As the component (E), an organic carboxylic acid is preferable, andsalicylic acid is particularly desirable.

The component (E) is typically used in an amount within a range from0.01 to 5.0 parts by weight, relative to 100 parts by weight of thecomponent (A).

If desired, other miscible additives can also be added to the positiveresist composition of the present invention. Examples of such miscibleadditives include additive resins for improving the performance of theresist film, surfactants for improving the applicability, dissolutioninhibitors, plasticizers, stabilizers, colorants, halation preventionagents, and dyes.

[Component (S)]

The positive resist composition of the present invention can be preparedby dissolving the materials for the resist composition in an organicsolvent (hereafter, frequently referred to as “component (S)”).

The component (S) may be any organic solvent which can dissolve therespective components to give a uniform solution, and one or more kindsof any organic solvent can be appropriately selected from those whichhave been conventionally known as solvents for a chemically amplifiedresist.

Examples thereof include lactones such as γ-butyrolactone; ketones suchas acetone, methyl ethyl ketone, cyclohexanone, methyl-n-pentyl ketone,methyl isopentyl ketone, and 2-heptanone; polyhydric alcohols, such asethylene glycol, diethylene glycol, propylene glycol and dipropyleneglycol; compounds having an ester bond, such as ethylene glycolmonoacetate, diethylene glycol monoacetate, propylene glycolmonoacetate, and dipropylene glycol monoacetate; polyhydric alcoholderivatives including compounds having an ether bond, such as amonoalkylether (e.g., monomethylether, monoethylether, monopropyletheror monobutylether) or monophenylether of any of these polyhydricalcohols or compounds having an ester bond (among these, propyleneglycol monomethyl ether acetate (PGMEA) and propylene glycol monomethylether (PGME) are preferable); cyclic ethers such as dioxane; esters suchas methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate,butyl acetate, methyl pyruvate, ethyl pyruvate, methylmethoxypropionate, and ethyl ethoxypropionate; and aromatic organicsolvents such as anisole, ethylbenzylether, cresylmethylether,diphenylether, dibenzylether, phenetole, butylphenylether, ethylbenzene,diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymeneand mesitylene.

These solvents can be used individually, or in combination as a mixedsolvent.

Among these, PGMEA, PGME, EL and γ-butyrolactone are preferable.

Further, among the mixed solvents, a mixed solvent obtained by mixingPGMEA with a polar solvent is preferable. The mixing ratio (weightratio) of the mixed solvent can be appropriately determined, taking intoconsideration the compatibility of the PGMEA with the polar solvent, butis preferably in the range of 1:9 to 9:1, more preferably from 2:8 to8:2.

Specifically, when EL is mixed as the polar solvent, the PGMEA:EL weightratio is preferably from 1:9 to 9:1, and more preferably from 2:8 to8:2. Alternatively, when PGME is mixed as the polar solvent, thePGMEA:PGME is preferably from 1:9 to 9:1, more preferably from 2:8 to8:2, and still more preferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of at least one of PGMEAand EL with γ-butyrolactone is also preferable. The mixing ratio(former:latter) of such a mixed solvent is preferably from 70:30 to95:5.

The amount of the organic solvent is not particularly limited, and isappropriately adjusted to a concentration which enables coating of acoating solution to a substrate, depending on the thickness of thecoating film. In general, the organic solvent is used in an amount suchthat the solid content of the resist composition becomes within therange from 0.5 to 20% by weight, and preferably from 1 to 15% by weight.

Dissolving of the resist materials in the component (S) can be conductedby simply mixing and stirring each of the above components togetherusing conventional methods, and where required, the composition may alsobe mixed and dispersed using a dispersion device such as a dissolver, ahomogenizer, or a triple roll mill. Furthermore, following mixing, thecomposition may also be filtered using a mesh, or a membrane filter orthe like.

<<Method of Forming a Resist Pattern>>

The method of forming a resist pattern according to a second aspect ofthe present invention includes: using a positive resist composition ofthe present invention to from a resist film on a substrate; conductingexposure of the resist film; and alkali-developing the resist film toform a resist pattern.

More specifically, the method for forming a resist pattern according tothe present invention can be performed, for example, as follows.

More specifically, the method for forming a resist pattern according tothe present invention can be performed, for example, as follows.Firstly, a positive resist composition of the present invention isapplied onto a substrate using a spinner or the like, and a prebake(post applied bake (PAB)) is conducted under temperature conditions of80 to 150° C. for 40 to 120 seconds, preferably 60 to 90 seconds to forma resist film. Then, for example, using an ArF exposure apparatus or thelike, the resist film is selectively exposed with an ArF exposureapparatus, an electron beam exposure apparatus, an EUV exposureapparatus or the like through a mask pattern or directly irradiated withelectron beam without a mask pattern, followed by post exposure bake(PEB) under temperature conditions of 80 to 150° C. for 40 to 120seconds, preferably 60 to 90 seconds. Subsequently, developing isconducted using an alkali developing solution such as a 0.1 to 10% byweight aqueous solution of tetramethylammonium hydroxide (TMAH),preferably followed by rinsing with pure water, and drying. If desired,bake treatment (post bake) can be conducted following the developing. Inthis manner, a resist pattern that is faithful to the mask pattern canbe obtained.

The substrate is not specifically limited and a conventionally knownsubstrate can be used. For example, substrates for electroniccomponents, and such substrates having wiring patterns formed thereoncan be used. Specific examples of the material of the substrate includemetals such as silicon wafer, copper, chromium, iron and aluminum; andglass. Suitable materials for the wiring pattern include copper,aluminum, nickel, and gold.

Further, as the substrate, any one of the above-mentioned substratesprovided with an inorganic and/or organic film on the surface thereofmay be used. As the inorganic film, an inorganic antireflection film(inorganic BARC) can be used. As the organic film, an organicantireflection film (organic BARC) and an organic film such as alower-layer organic film used in a multilayer resist method can be used.

Here, a “multilayer resist method” is method in which at least one layerof an organic film (lower-layer organic film) and at least one layer ofa resist film (upper resist film) are provided on a substrate, and aresist pattern formed on the upper resist film is used as a mask toconduct patterning of the lower-layer organic film. This method isconsidered as being capable of forming a pattern with a high aspectratio. More specifically, in the multilayer resist method, a desiredthickness can be ensured by the lower-layer organic film, and as aresult, the thickness of the resist film can be reduced, and anextremely fine pattern with a high aspect ratio can be formed.

The multilayer resist method is broadly classified into a method inwhich a double-layer structure consisting of an upper-layer resist filmand a lower-layer organic film is formed (double-layer resist method),and a method in which a multilayer structure having at least threelayers consisting of an upper-layer resist film, a lower-layer organicfilm and at least one intermediate layer (thin metal film or the like)provided between the upper-layer resist film and the lower-layer organicfilm (triple-layer resist method).

The wavelength to be used for exposure is not particularly limited andthe exposure can be conducted using radiation such as ArF excimer laser,KrF excimer laser, F₂ excimer laser, extreme ultraviolet rays (EUV),vacuum ultraviolet rays (VUV), electron beam (EB), X-rays, and softX-rays. The positive resist composition of the present invention iseffective to KrF excimer laser, ArF excimer laser, EB and EUV, andparticularly effective to ArF excimer laser.

The exposure of the resist film can be either a general exposure (dryexposure) conducted in air or an inert gas such as nitrogen, orimmersion exposure (immersion lithography).

In immersion lithography, the region between the resist film and thelens at the lowermost point of the exposure apparatus is pre-filled witha solvent (immersion medium) that has a larger refractive index than therefractive index of air, and the exposure (immersion exposure) isconducted in this state.

The immersion medium preferably exhibits a refractive index larger thanthe refractive index of air but smaller than the refractive index of theresist film to be exposed. The refractive index of the immersion mediumis not particularly limited as long at it satisfies the above-mentionedrequirements.

Examples of this immersion medium which exhibits a refractive index thatis larger than the refractive index of air but smaller than therefractive index of the resist film include water, fluorine-based inertliquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquidscontaining a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃,C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling pointwithin a range from 70 to 180° C. and preferably from 80 to 160° C. Afluorine-based inert liquid having a boiling point within theabove-mentioned range is advantageous in that the removal of theimmersion medium after the exposure can be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which allof the hydrogen atoms of the alkyl group are substituted with fluorineatoms is particularly desirable. Examples of these perfluoroalkylcompounds include perfluoroalkylether compounds and perfluoroalkylaminecompounds.

Specifically, one example of a suitable perfluoroalkylether compound isperfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and anexample of a suitable perfluoroalkylamine compound isperfluorotributylamine (boiling point 174° C.).

As the immersion medium, water is preferable in terms of cost, safety,environment and versatility.

The method of forming a resist pattern according to the presentinvention is also applicable to a double exposure method or a doublepatterning method.

As described hereinabove, by the positive resist composition and methodof forming a resist pattern according to the present invention, a resistfilm exhibiting an excellent hydrophobicity on the film surface can beformed.

A resist film formed using the positive resist composition of thepresent invention contains the fluorine-containing polymeric compound(F1) having the structural unit (f1).

As described above, since the component (F1) contains a fluorine atom, aresist film formed using the positive resist composition exhibits a highhydrophobicity, as compared to the case where a positive resistcomposition which does not contain the fluorine-containing polymericcompound is used.

Thus, a resist film formed using the positive resist composition of thepresent invention exhibits a high hydrophobicity during immersionexposure, as compared to the case of using a conventional resistcomposition. Therefore, the resist film exhibits an excellent watertracking ability (tracking ability of water with respect to the movementof the lens) which is required when immersion exposure is conductedusing a scanning-type immersion exposure apparatus as disclosed inNon-Patent Document 1, and a high scanning speed can be achieved.

In a resist film formed using the positive resist composition of thepresent invention, by virtue of using the component (F1) and thecomponent (A1), the hydrophobicity of the resist film is enhanced ascompared to the case where a conventional positive resist composition isused, and the contact angles against water, e.g., the static contactangle (the contact angle between the surface of a water droplet on theresist film in a horizontal state and the resist film surface), thedynamic contact angle (the contact angle at which a water droplet startsto slide when the resist film is inclined, including the contact angleat the front-end point of the water droplet in the sliding direction(advancing angle) and the contact angle at the rear-end point of thewater droplet in the sliding direction (receding angle)) and slidingangle (the inclination angle at which a water droplet starts to slidewhen the resist film is inclined) are changed. For example, the higherthe hydrophobicity of a resist film, the higher the static contact angleand the dynamic contact angle and the smaller the sliding angle.

FIG. 1 is an explanatory diagram of an advancing angle (θ₁), a recedingangle (θ₂) and a sliding angle (θ₃).

As shown in FIG. 1, when a droplet 1 is placed on a plane 2 and theplane 2 is gradually inclined, the advancing angle is the angle θ₁formed between the lower end 1 a of the droplet 1 and the plane 2 as thedroplet 1 starts to move (slide) on the plane 2.

Further, at this point (the point when the liquid droplet 1 starts tomove (slide) down the flat surface 2), the angle θ₂ between the surfaceof the liquid droplet at the top edge 1 b of the liquid droplet 1 andthe flat surface 2 is the receding angle, and the inclination angle θ₃of the flat surface 2 is the sliding angle.

In the present description, the static contact angle, the dynamiccontact angle and the sliding angle are measured in the followingmanner.

First, a resist composition solution is spin-coated onto a siliconsubstrate, and then heated under predetermined conditions, for example,at a temperature of 110° C. to 115° C. for 60 seconds to form a resistfilm.

Subsequently, the contact angles can be measured using commerciallyavailable measurement apparatuses such as DROP MASTER-700 (product name;manufactured by Kyowa Interface Science Co. Ltd.), AUTO SLIDING ANGLE:SA-30 DM (product name; manufactured by Kyowa Interface Science Co.Ltd.), and AUTO DISPENSER: AD-31 (product name; manufactured by KyowaInterface Science Co. Ltd.).

With respect to the positive resist composition of the presentinvention, the measured value of the receding angle of a resist filmformed using the positive resist composition is preferably 70 degrees(°) or more, more preferably 73° or more, and still more preferably 75°or more. The larger the receding angle, the higher the hydrophobicity ofthe resist film surface, thereby enabling high-speed scanning duringimmersion exposure. Further, the effect of suppressing elution of asubstance (leaching) can be improved. It is presumed that one of themain reasons why these effects can be achieved is related to thehydrophobicity of the resist film. More specifically, it is presumedthat, since an aqueous substance such as water is used as the immersionmedium, higher hydrophobicity has an influence on the swift removal ofthe immersion medium from the surface of the resist film after theimmersion exposure. The upper limit value of the receding angle is notparticularly limited, and can be, for example, 90° or less.

For the same reasons as described above, with respect to a resist filmformed using the positive resist composition of the present invention,it is particularly desirable that the static contact angle as measuredprior to conducting exposure and development is 80 to 100°.

Further, with respect to a resist film formed using the positive resistcomposition of the present invention, the sliding angle as measuredprior to exposure and development is preferably 25° or less, and morepreferably 20° or less. When the sliding angle is no more than the upperlimit of the above-mentioned range, the effect of suppressing theelution of a substance during immersion exposure is enhanced. The lowerlimit of the sliding angle is not particularly limited, and can be, forexample, 5° or more.

Furthermore, with respect to a resist film formed using the positiveresist composition of the present invention, the advancing angle asmeasured prior to exposure and development is preferably 80 to 100°, andmore preferably 80 to 90°. When the advancing angle is within theabove-mentioned range, various lithography properties can be improved,e.g., the risk of defect generation can be reduced.

The level of the above-mentioned various contact angles (static contactangle, dynamic contact angle and sliding angle) can be adjusted by theformulation of the positive resist composition, e.g., the type of thecomponent (A1), the amount of the structural unit (a0) within thecomponent (A), the type of the component (F1), the amount of thecomponent (F1), and the like. For example, the larger the amount of thestructural unit (a0) within the component (A) or the amount of thecomponent (F1), the higher the hydrophobicity of the resist film formed.In particular, the receding angle becomes larger. Further, inparticular, by adjusting the amount of the component (F1) and the amountof fluorine contained in the structural unit(s), the advancing angle canbe adjusted (the smaller the amount of fluorine, the smaller theadvancing angle).

In addition, by using the positive resist composition of the presentinvention, elution of a substance (leaching) from the resist film duringimmersion exposure can be suppressed.

As described above, immersion exposure is a method in which exposure(immersion exposure) is conducted in a state where the region betweenthe lens and the resist layer formed on a wafer (which wasconventionally filled with air or an inert gas such as nitrogen) isfilled with a solvent (a immersion medium) that has a larger refractiveindex than the refractive index of air. In immersion exposure, when theresist film comes into contact with the immersion medium, elution ofsubstances within the resist film (component (B), component (D), and thelike) into the immersion medium occurs. This elution of a substancecauses phenomenon such as degeneration of the resist film and change inthe refractive index of the immersion medium, thereby adverselyaffecting the lithography properties.

The amount of the eluted substance is affected by the properties of theresist film surface (e.g., hydrophilicity, hydrophobicity, and thelike). Therefore, it is presumed that the amount of eluted substance canbe reduced by enhancing the hydrophobicity of the resist film surface.

Since a resist film formed using the positive resist composition of thepresent invention includes the component (F1), the resist film exhibitshigh hydrophobicity prior to conducting exposure and developing, ascompared to a resist composition which does not contain the component(F1). Thus, by the positive resist composition of the present invention,elution of a substance during immersion exposure can be suppressed.

Since elution of a substance can be suppressed, by using the positiveresist composition of the present invention, phenomenon such asdegeneration of the resist film and change in the refractive index ofthe immersion medium, which occur during immersion exposure, can besuppressed. Further, as variation in the refractive index of theimmersion medium can be suppressed, a resist pattern having an excellentshape can be formed. Furthermore, the level of contamination of the lenswithin the exposure apparatus can be lowered. Therefore, there is noneed for protection against these disadvantages, and hence, the presentinvention can contribute to simplifying the process and the exposureapparatus.

Moreover, the positive resist composition of the present inventioncontains the component (F1) including the structural unit (f1) having analkali developing solution decomposable group.

In the present invention, for example, when the structural unit (f1) isa structural unit represented by the aforementioned general formula(f1-1), the “—O—R⁰” group in formula (f1-1) may be a group that isdissociable by the action of a base (alkali developing solution).Alternatively, the structural unit (f1) may be a structural unitrepresented by the aforementioned general formula (f1-1) in which theester bond “—C(═O)—O—” in general formula (f1-0) is decomposable(hydrolyzable) by the action of a base (alkali developing solution) toform a hydrophilic group “—C(═O)—OH”. In such a case, the component (F1)becomes decomposable in an alkali developing solution. The expression“decomposable in an alkali developing solution” means that the group isdecomposable by the action of an alkali developing solution (preferablydecomposable by action of a 2.38% by weight aqueous solution oftetramethylammonium hydroxide (TMAH) at 23° C.), and exhibits increasedalkali solubility in the alkali developing solution. The component (F1)is a compound that is hardly soluble in an alkali developing solutionprior to decomposition, and when the component (F1) is decomposed byaction of the developing solution, a carboxy group which is ahydrophilic group is formed, thereby exhibiting increased solubility inthe alkali developing solution.

By using the positive resist composition of the present inventioncontaining the component (F1), a resist pattern can be formed which ishydrophobic prior to coming in contact with an alkali developingsolution (e.g., during immersion exposure), and becomes hydrophilicduring alkali developing. Especially when the portion hydrolyzed by theaction of an alkali developing solution has a fluorine atom, because theportion containing a fluorine atom is dissociated, the effect forincreasing the hydrophilicity is enhanced.

Furthermore, when the structural unit (f1) is block copolymerized, theportion containing a fluorine atom is localized, as compared to when thestructural unit (f1) is random polymerized. As a result, hydrophobicityis enhanced prior to development, and after development, since thehydrophilic group formed by hydrolysis is localized, hydrophilicity isenhanced. Thus, the effect of enhancing hydrophilicity after developmentis further improved.

By using such a positive resist composition in which the hydrophilicityis enhanced during alkali developing, generation of defects duringimmersion exposure (especially defects caused by a deposit generatedafter the development process) can be effectively suppressed. Thereasons for these effects are explained below.

In an immersion exposure process, it is preferable to enhance thehydrophobicity of the resist film so as to prevent the resist film frombeing affected by the immersion medium such as water.

However, when the hydrophobicity of the resist film is high, it isdisadvantageous in that the risk of defects caused by a depositgenerated after the development process becomes high. The reason forthis is that the deposit is a residue which was not washed off theresist film by the hydrophilic developing solution and remaining on theresist film. Since this deposit is hydrophobic, the deposit becomeseasier to be adhered to the resist film as the hydrophobicity of theresist film becomes higher.

In view of the above, the resist film is required to be hydrophobicduring immersion exposure and become hydrophilic during alkalideveloping.

As described above, the component (F1) according to the presentinvention is decomposable by an alkali developing solution. Therefore,it becomes possible to form a resist film that is hydrophobic prior tocoming in contact with an alkali developing solution (e.g., duringimmersion exposure), and becomes hydrophilic during alkali developing.

In the conventional techniques, when a resist film exhibits highhydrophobicity, defects (e.g., water mark defects caused by theimmersion medium such as water or an alkali developing solution andother defects including bridge-type defects and “Not Open” defects inwhich portion of, or all of, a hole pattern is not open) are likely tobe formed on the surface of resist patterns following developing. Incontrast, because a resist film formed using the resist composition ofthe present invention exhibits increased hydrophilicity after alkalideveloping, it becomes possible to reduce the occurrence of thesedefects. Moreover, the effect of enhancing hydrophilicity afterdevelopment is not limited to immersion exposure, and is effective inimproving defects in any exposure process including a development stepusing an alkali developing solution.

Thus, the positive resist composition of the present invention iscapable of effectively reducing defects (especially defects caused by adeposit generated after the development process), and is very useful inan immersion exposure process.

Further, when the component (F1) has a structural unit represented bygeneral formula (f1-1) for example, since the structural unit has acarbonyloxy group (—C(═O)—O—) exhibiting a relatively high polarity, thecomponent (F1) exhibits improved compatibility with other components ofthe resist composition. Therefore, the positive resist composition ofthe present invention is expected to exhibit improved stability overtime.

In addition, a resist film formed using the positive resist compositionof the present invention hardly swells due to being exposed to water.Therefore, a very fine resist pattern can be formed with a highprecision.

Also, the positive resist composition of the present invention exhibitsexcellent lithography properties with respect to sensitivity,resolution, etching resistance and the like, and is capable of forming aresist pattern without any practical problems when used as a resist forimmersion exposure. For example, by using the positive resistcomposition of the present invention, a very fine resist pattern with asize of 65 nm or smaller can be formed. Thus, the positive resistcomposition of the present invention exhibits excellent lithographyproperties, and is capable of forming a resist pattern without anypractical problems when used as a resist for immersion exposure. Morespecifically, the positive resist composition of the present inventionexhibits not only excellent lithography properties generally required(sensitivity, resolution, etching resistance, and the like), but alsoexcellent properties required for a resist material used in immersionexposure (hydrophobicity, ability of suppressing elution of a substance,water tracking ability, and the like). Therefore, the positive resistcomposition of the present invention is preferable for use in immersionexposure.

Furthermore, by virtue of the aforementioned features, thefluorine-containing polymeric compound (F1) is useful as an additive fora resist composition.

There are no particular limitations on the resist composition containingthe added fluorine-containing compound, although a chemically amplifiedresist composition including a base component that exhibits changedsolubility in an alkali developing solution under the action of acid,and an acid generator component that generates acid upon irradiation isideal.

EXAMPLES Synthesis of Fluorine-Containing Compound Component (F)

The fluorine-containing polymeric compounds used as thefluorine-containing compound component (F) in the present examples weresynthesized in accordance with the following polymer synthesis examples.

Synthesis Example 1 Synthesis of Fluorine-Containing Compound (1) (i)Synthesis of Compound (1)-2

61 g (600 mmol) of triethylamine and 64 g (418 mmol) of methylbromoacetate were added to 300 ml of a THF solution containing 30 g (348mmol) of methacrylic acid in a nitrogen atmosphere at 0° C., and thetemperature was elevated to room temperature, followed by stirring for 3hours. After conducting thin-layer chromatography (TLC) to confirm thatthe raw materials had dissipated, the reaction solution was subjected todistillation under reduced pressure to remove the solvent. Then, waterwas added to the resultant, and extraction was conducted with ethylacetate three times. The resulting organic phase was washed with watertwice, and then subjected to distillation under reduced pressure toremove the solvent, thereby obtaining 47 g of a compound (1)-1 in theform of a colorless liquid (yield: 85%).

Subsequently, 700 ml of a THF solution containing 30 g (190 mmol) of thecompound (1)-1 was prepared, and 700 ml of a 2.38% by weight aqueoussolution of TMAH was added thereto, followed by stirring at roomtemperature for 3 hours. After conducting thin-layer chromatography(TLC) to confirm that the raw materials had dissipated, THF wasdistilled off under reduced pressure. Then, the resulting aqueousreaction solution was cooled to 0° C., and 50 ml of a 10N hydrochloricacid was added thereto to render the aqueous reaction solution acidic,followed by extraction with ethyl acetate three times. The resultingorganic phase was washed with water twice, and the solvent was distilledoff under reduced pressure, thereby obtaining 26 g of a compound (1)-2shown below in the form of a colorless liquid (yield: 95%).

The obtained compounds (1)-1 and (1)-2 were analyzed by ¹H-NMR. Theresults are shown below.

Spectrum Data of Compound (1)-1

¹H-NMR(CDCl₃) 6.23(s,1H,Hb), 5.67(d,1H,Hb), 4.13(s,2H,Hc),3.78(s,3H,Hd), 2.00(s,3H,Ha)

Spectrum Data of Compound (1)-2

¹H-NMR(CDCl₃) 6.23(s,1H,Hb), 5.67(d,1H,Hb), 4.69(s,2H,Hc), 2.00(s,3H,Ha)

(ii) Synthesis of Fluorine-Containing Compound (1)

26 g (180.39 mmol) of a compound (1)-2 was added to 200 ml of a THFsolution containing 23.48 g (234.5 mmol) of 2,2,2-trifluoroethanol, 51.9g (270.6 mmol) of ethyldiisopropylaminocarbodiimide (EDC1) hydrochlorideand 0.11 g (0.9 mmol) of dimethylaminopyridine (DMAP) in a nitrogenatmosphere at 0° C., and the temperature was elevated to roomtemperature, followed by stirring for 3 hours. After conductingthin-layer chromatography (TLC) to confirm that the raw materials haddissipated, the reaction solution was cooled to 0° C., and water wasadded thereto to stop the reaction. Then, extraction was conducted withethyl acetate three times, and the obtained organic phase was washedwith water twice. Thereafter, the solvent was distilled off underreduced pressure to obtain a crude product, and the obtained crudeproduct was purified by silica gel filtration (using ethyl acetate),thereby obtaining 25 g of a fluorine-containing compound (1) shown belowin the form of a colorless liquid.

The obtained fluorine-containing compound (1) was analyzed by ¹H-NMR.The results are shown below.

¹H-NMR(CDCl₃) 6.24(s,1H,Hb), 5.70(s,1H,Hb), 4.80(s,2H,Hc),4.60-4.51(m,2H,Hd), 1.99(s,3H,Ha)

From the results shown above, it was confirmed that thefluorine-containing compound (1) had a structure shown below.

Synthesis Example 2 Synthesis of Fluorine-Containing Compound (2)

25 g (125 mmol) of a compound (2-1) shown below was added to 200 ml of aTHF solution containing 30.1 g (200 mmol) of2,2,3,3,3-pentafluoropropanol, 47.9 g (250 mmol) ofethyldiisopropylaminocarbodiimide (EDCI) hydrochloride and 1.0 g ofdimethylaminopyridine (DMAP) in a nitrogen atmosphere at 0° C., and thetemperature was elevated to room temperature, followed by stirring for 3hours. After conducting thin-layer chromatography (TLC) to confirm thatthe raw materials had dissipated, the reaction solution was cooled to 0°C., and water was added thereto to stop the reaction. Then, extractionwas conducted with ethyl acetate three times, and the obtained organicphase was washed with water twice. Thereafter, the solvent was distilledoff under reduced pressure to obtain a crude product, and the obtainedcrude product was purified by silica gel filtration (using ethylacetate), thereby obtaining 22 g of a fluorine-containing compound (2)shown below in the form of a colorless liquid.

The obtained fluorine-containing compound (2) was analyzed by ¹H-NMR.The results are shown below.

¹H-NMR(CDCl₃)[ppm]: 6.16(s,1H,Hb), 5.50(s,1H,Hb), 4.57(t,2H,Hd),1.92(s,3H,Ha), 1.65(s,6H,Hc)

Synthesis Example 3 Synthesis of Fluorine-Containing Polymeric Compound(1): Synthesis of Block Copolymer

In a glove box purged with nitrogen, 0.333 g ofethyl-2-methyl-2-butyltellanyl-propionate, 0.205 g of dibutyltellunide,0.091 g of azobisisobutyronitrile, 9.96 g of the fluorine-containingcompound (1) and 12.17 g of 1,4-dioxane were added to a reaction vessel,and a polymerization reaction was performed at 65° C. for 10 hours.

Subsequently, a mixture containing 10.04 g of a compound (5) shownbelow, 12.27 g of 1,4-dioxane and 0.023 g of azobisbutyronitrile wasdropwise added to the reaction system, and the reaction was continuedfor 12 hours.

Thereafter, 22.23 g of 1,4-dioxane was added thereto, and the reactionmixture was heated to 80° C. while stirring. While maintaining thetemperature at 80° C., a mixed solution containing 4.02 g of 1,4-dioxaneand 2.01 g of a 30% oxygenated water was dropwise added thereto over 1hour. After the dropwise addition, the resultant was stirred at 80° C.for 12 hours.

The reaction solution was cooled, and diluted with 91 g of ethylacetate. Then, the organic phase was washed with 55 g of a 3% aqueousoxalic acid in a separatory funnel, followed by washing with 55 g of ionexchanged water 4 times to wash the organic phase with a total of 220 gof ion exchanged water. The resultant was poured to 1,000 g of a hexanesolution of the organic phase, and the formed precipitate was separatedby filtration. The collected precipitate was dried under reducedpressure, thereby obtaining 14.3 g of the desired fluorine-containingpolymeric compound shown below.

The obtained polymer was analyzed by GPC. As a result, it was found thatMn=12,500, and Mw/Mn=1.38.

Further, as a result of C-NMR analysis, it was found that the polymercompositional ratio was f₁₁₁:f₂=49:51

Synthesis Example 4 Synthesis of Fluorine-Containing Polymeric Compound(2): Synthesis of Partial Block Copolymer

In a glove box purged with nitrogen, 0.345 g ofethyl-2-methyl-2-butyltellanyl-propionate, 0.212 g of dibutyltellunide,0.094 g of azobisisobutyronitrile, 6.93 g of the fluorine-containingcompound (1) and 8.47 g of 1,4-dioxane were added to a reaction vessel,and a polymerization reaction was performed at 65° C. for 5 hours.

Subsequently, a mixture containing 11.45 of the compound (1), 4.62 g ofthe compound (5), 19.64 g of 1,4-dioxane and 0.024 g ofazobisbutyronitrile was dropwise added to the reaction system, and thereaction was continued for 17 hours.

Thereafter, 22.23 g of 1,4-dioxane was added thereto, and the reactionmixture was heated to 80° C. while stirring. While maintaining thetemperature at 80° C., a mixed solution containing 3.63 g of 1,4-dioxaneand 1.81 g of a 30% oxygenated water was dropwise added thereto over 1hour. After the dropwise addition, the resultant was stirred at 80° C.for 12 hours.

The reaction solution was cooled, and diluted with 105 g of ethylacetate. Then, the organic phase was washed with 64 g of a 3% aqueousoxalic acid in a separatory funnel, followed by washing with 64 g of ionexchanged water 4 times to wash the organic phase with a total of 256 gof ion exchanged water. The resultant was poured to 1,150 g of a hexanesolution of the organic phase, and the formed precipitate was separatedby filtration. The collected precipitate was dried under reducedpressure, thereby obtaining 10.0 g of the desired fluorine-containingpolymeric compound (2) shown below.

The obtained polymer was analyzed by GPC. As a result, it was found thatMn=15,900, and Mw/Mn=1.14.

Further, as a result of C-NMR analysis, it was found that the polymercompositional ratio was f₁₁₁:f₂=41:59

Synthesis Example 5 Synthesis for Comparative Example

20.00 g (88.44 mmol) of the fluorine-containing compound (1) and 6.60 g(29.48 mmol) of the compound (5) were added to a three-necked flaskequipped with a thermometer and a reflux tube and were dissolved byadding 39.90 g of tetrahydrofuran thereto. Then, 23.58 mmol of dimethyl2,2′-azobis(isobutyrate) (V-601) as a polymerization initiator was addedand dissolved in the resulting solution. The resulting solution wasdropwise added to 22.17 g of tetrahydrofuran that was heated to 67° C.under a nitrogen atmosphere over 3 hours, and was then subjected to apolymerization reaction. The resulting reaction solution was heatedwhile stirring for 4 hours, and then cooled to room temperature. Theresulting polymer solution was dropwise added to an excess amount ofn-heptane to precipitate a polymer. Then, the precipitated polymer wasseparated by filtration, followed by washing and drying, therebyobtaining 13 g of a fluorine-containing polymeric compound (11) shownbelow as an objective compound.

With respect to the fluorine-containing polymeric compound (11), theweight average molecular weight and the dispersity were determined bythe polystyrene equivalent value as measured by gel permeationchromatography (GPC). As a result, it was found that the weight averagemolecular weight (Mw) was 13,800, and the dispersity (Mw/Mn) was 1.50.Further, as a result of an analysis by carbon 13 nuclear magneticresonance spectroscopy (600 MHz, ¹³C-NMR), it was found that thecomposition of the copolymer (ratio (molar ratio) of the respectivestructural units within the structural formula) was f₁₁₁/f₂=77.6/22.4.

Each polymeric compound shown in Table 1 were synthesized in the manneras described above.

TABLE 1 Synthesis method Block synthesis portion Random synthesisportion Mw Mw/Mn Fluorine-containing Synthesis Fluorine-containingCompound (5) 17000 1.54 polymeric compound 1 Example 3 compound (1)[19.8] [80.2] Fluorine-containing Synthesis Fluorine-containing Compound(5) 12500 1.38 polymeric compound 2 Example 3 compound (1) [49] [51]Fluorine-containing Synthesis Fluorine-containing Compound (5) 140001.28 polymeric compound 3 Example 3 compound (1) [79.6] [20.4]Fluorine-containing Synthesis Fluorine-containing Compound (5) 160001.40 polymeric compound 4 Example 3 compound (2) [19.5] [80.5]Fluorine-containing Synthesis Fluorine-containing Compound (5)Fluorine-containing 16000 1.14 polymeric compound 5 Example 4 compound(1) [19.5] compound (1) [60.1] [20.4] Fluorine-containing SynthesisFluorine-containing Compound (5) Compound (6) 17500 1.48 polymericcompound 6 Example 4 compound (1) [15.8] [7.9] [76.3]Fluorine-containing Synthesis Fluorine-containing Compound (5) Compound(7) 15500 1.27 polymeric compound 7 Example 4 compound (1) [46.8] [20.1][33.1] Fluorine-containing Synthesis Fluorine-containing Compound (5)Compound (8) 15000 1.24 polymeric compound 8 Example 4 compound (1)[50.3] [23.5] [26] Fluorine-containing Synthesis Fluorine-containingCompound (5) 16000 1.31 polymeric compound 9 Example 3 compound (3)[24.4] [75.6] Fluorine-containing Synthesis Fluorine-containing Compound(5) 17000 1.35 polymeric compound 10 Example 3 compound (4) [19.4][80.6] Fluorine-containing Synthesis Fluorine-containing Compound (5)18000 1.59 polymeric compound 11 Example 5 compound (1) [23.2] [76.8]

In Table 1, the reference characters indicate the following. Further,the values in brackets [ ] indicate the amount (mol %) of the respectivestructural units.

Compounds (3), (4), (6) to (8): compounds represented by chemicalformulas shown below

Examples 1 to 14, Comparative Examples 1 to 5

The components shown in Tables 2 and 3 were mixed together and dissolvedto obtain positive resist compositions.

TABLE 2 Compo- Compo- Compo- Compo- Compo- nent nent nent nent nent (A)(B) (D) (F) (S) Ex. 1 (A)-1 (B)-1 (D)-1 (F)-1 (S)-1 (S)-2 [100] [10][0.3] [0.5] [2500] [10] Ex. 2 (A)-1 (B)-1 (D)-1 (F)-1 (S)-1 (S)-2 [100][10] [0.3] [1] [2500] [10] Ex. 3 (A)-1 (B)-1 (D)-1 (F)-1 (S)-1 (S)-2[100] [10] [0.3] [3] [2500] [10] Ex.. 4 (A)-1 (B)-1 (D)-1 (F)-1 (S)-1(S)-2 [100] [10] [0.3] [100] [2500] [10] Ex. 5 (A)-1 (B)-1 (D)-1 (F)-2(S)-1 (S)-2 [100] [10] [0.3] [0.5] [2500] [10] Ex. 6 (A)-1 (B)-1 (D)-1(F)-2 (S)-1 (S)-2 [100] [10] [0.3] [1] [2500] [10] Ex. 7 (A)-1 (B)-1(D)-1 (F)-2 (S)-1 (S)-2 [100] [10] [0.3] [3] [2500] [10] Ex. 8 (A)-1(B)-1 (D)-1 (F)-2 (S)-1 (S)-2 [100] [10] [0.3] [100] [2500] [10] Ex. 9(A)-1 (B)-1 (D)-1 (F)-5 (S)-1 (S)-2 [100] [10] [0.3] [3] [2500] [10] Ex.10 (A)-1 (B)-1 (D)-1 (F)-6 (S)-1 (S)-2 [100] [10] [0.3] [3] [2500] [10]Ex. 11 (A)-1 (B)-1 (D)-1 (F)-7 (S)-1 (S)-2 [100] [10] [0.3] [3] [2500][10] Ex. 12 (A)-1 (B)-1 (D)-1 (F)-9 (S)-1 (S)-2 [100] [10] [0.3] [3][2500] [10] Ex. 13 (A)-1 (B)-1 (D)-1  (F)-10 (S)-1 (S)-2 [100] [10][0.3] [3] [2500] [10] Comp. (A)-1 (B)-1 (D)-1 — (S)-1 (S)-2 Ex. 1 [100][10] [0.3] [2500] [10] Comp. (A)-1 (B)-1 (D)-1  (F)-11 (S)-1 (S)-2 Ex. 2[100] [10] [0.3] [0.5] [2500] [10] Comp. (A)-1 (B)-1 (D)-1  (F)-11 (S)-1(S)-2 Ex. 3 [100] [10] [0.3] [1] [2500] [10] Comp. (A)-1 (B)-1 (D)-1 (F)-11 (S)-1 (S)-2 Ex. 4 [100] [10] [0.3] [3] [2500] [10]

TABLE 3 Compo- Compo- Compo- Compo- Compo- nent nent nent nent nent (A)(B) (D) (F) (S) Ex. 14 (A)-2 (A)-3 (B)-2 (B)-3 (D)-1 (F)-1 (S)-1 (S)-2[85] [15] [6.7] [2.6] [0.6] [3] [2500] [10] Comp. (A)-2 (A)-3 (B)-2(B)-3 (D)-1  (F)-11 (S)-1 (S)-2 Ex. 5 [85] [15] [6.7] [2.6] [0.6] [3][2500] [10]

In Tables 2 and 3, the reference characters indicate the following.Further, the values in brackets [ ] indicate the amount (in terms ofparts by weight) of the component added.

(A)-1: a copolymer represented by chemical formula (A)-1 shown below,having an Mw of 8,000 and Mw/Mn of 1.65. In the formula, the subscriptnumerals shown to the bottom right of the parentheses ( ) indicate thepercentage (mol %) of the respective structural units within thecopolymer.

(A)-2: a copolymer represented by chemical formula (A)-2 shown below,having an Mw of 10,000 and Mw/Mn of 1.70. In the formula, the subscriptnumerals shown to the bottom right of the parentheses ( ) indicate thepercentage (mol %) of the respective structural units within thecopolymer.

(A)-3: a copolymer represented by chemical formula (A)-3 shown below,having an Mw of 7,000 and Mw/Mn of 1.65. In the formula, the subscriptnumerals shown to the bottom right of the parentheses ( ) indicate thepercentage (mol %) of the respective structural units within thecopolymer.

(B)-1: a compound represented by chemical formula (B)-1 shown below.

(B)-2: a compound represented by chemical formula (B)-2 shown below

(B)-3: a compound represented by chemical formula (B)-3 shown below

(D)-1: tri-n-pentylamine

(S)-1: a mixed solvent of PGMEA/PGME=6/4 (weight ratio)

(S)-2: γ-butyrolactone

(F)-1: the aforementioned [fluorine-containing polymeric compound 1]

(F)-2: the aforementioned [fluorine-containing polymeric compound 2]

(F)-3: the aforementioned [fluorine-containing polymeric compound 3]

(F)-4: the aforementioned [fluorine-containing polymeric compound 4]

(F)-5: the aforementioned [fluorine-containing polymeric compound 5]

(F)-6: the aforementioned [fluorine-containing polymeric compound 6]

(F)-7: the aforementioned [fluorine-containing polymeric compound 7]

(F)-8: the aforementioned [fluorine-containing polymeric compound 8]

(F)-9: the aforementioned [fluorine-containing polymeric compound 9]

(F)-10: the aforementioned [fluorine-containing polymeric compound 10]

(F)-11: the aforementioned [fluorine-containing polymeric compound 11]

(D)-1: tri-n-pentylamine

(S)-1: a mixed solvent of PGMEA/PGME=6/4 (weight ratio)

(S)-2: γ-butyrolactone

[Measurement of Contact Angle of Resist Film]

Using a spinner, each resist composition solution obtained in Examples 1to 13 and Comparative Examples 1 to 4 was applied to an 8-inch siliconwafer that had been treated with hexamethyldisilazane (HMDS), and thesolution was then prebaked and dried on a hotplate at 110° C. for 60seconds, thus forming a resist film with a film thickness of 100 nm.

A water droplet was dripped onto the surface of each resist film (theresist film prior to exposure), and a DROP MASTER-700 apparatus (productname; manufactured by Kyowa Interface Science Co. Ltd.) was used tomeasure the static contact angle and dynamic contact angle (recedingangle) (contact angle measurement: water 2 μl). The measured value wasdefined as the “contact angle after application (°)”.

Following measurement of the contact angle, the wafer was subjected toan alkali developing treatment for 30 seconds at 23° C. in a 2.38% byweight aqueous solution of tetramethylammonium hydroxide (TMAH). Thewafer was then rinsed with pure water for 15 seconds, followed by dryingby shaking. Subsequently, the contact angles were measured in the samemanner as described above. The measured values were defined as the“contact angle (°) after development”.

The results are shown in Table 4.

TABLE 4 Contact angle Conact angle after application after developmentStatic contact Receding Static contact Receding angle angle angle angle(°) (°) (°) (°) Comp. Ex. 1 72.8 61.7 70 52.8 Comp. Ex. 2 80.8 68.3 63.436.8 Comp. Ex. 3 84 71.7 60.9 28.9 Comp. Ex. 4 88.8 74 59.5 29 Comp. Ex.5 88.2 73.5 59.2 28.6 Ex. 1 81.2 71.2 49.1 23.4 Ex. 2 83.7 72.2 47.821.2 Ex. 3 86.5 75.2 45.6 16.9 Ex. 4 88.7 71.4 46.5 16.4 Ex. 5 80.5 68.560.3 29.7 Ex. 6 82.8 70 59.2 28.3 Ex. 7 87.5 74.5 50.3 20 Ex. 8 88.271.7 50.2 17.6 Ex. 9 85.6 70.1 47.6 23.1 Ex. 10 86.3 74.3 52.4 25.8 Ex.11 82.6 68.3 53.9 25.6 Ex. 12 87.6 74.5 48.1 23.1 Ex. 13 92.7 84.8 52.525.8 Ex. 14 88.4 74.1 45.6 16.4

As is evident from the above results shown in Table 4, the resist filmsformed using the resist compositions of Examples 1 to 13 which includedthe fluorine-containing polymeric compounds according to the presentinvention exhibited a high contact angle prior to development, ascompared to the resist films formed using the resist compositions ofComparative Examples 1 to 4 which did not include thefluorine-containing polymeric compound. Therefore, it was found that byvirtue of including a fluorine-containing compound of the presentinvention, the hydrophobicity of the resist film is enhanced. As aresult, it is expected that not only can the water tracking abilityduring immersion exposure using a scanning-type immersion exposureapparatus be improved, but also elution of a substance can besuppressed. Further, from the results of decrease in the contact angleand receding angle after development, it was confirmed thathydrophilicity is enhanced.

[Formation of Resist Pattern]

An organic anti-reflection film composition (product name: ARC29A,manufactured by Brewer Science Ltd.) was applied to an 12-inch siliconwafer using a spinner, and the composition was then baked at 205° C. for60 seconds, thereby forming an organic anti-reflection film having afilm thickness of 89 nm.

Then, each of the resist compositions of Examples 14 and ComparativeExample 5 was applied onto the anti-reflection film using a spinner, andwas then prebaked (PAB) on a hotplate at 110° C. for 60 seconds anddried, thereby forming a resist film having a film thickness of 100 nm.

Subsequently, the resist film was selectively irradiated with an ArFexcimer laser (193 nm) through a mask pattern, using an ArF immersionexposure apparatus NSR-S609B (manufactured by Nikon Corporation, NA(numerical aperture)=1.07, σ0.97). Thereafter, a post exposure bake(PEB) treatment was conducted at 100° C. for 60 seconds, followed byalkali development at 23° C. in a 2.38% by weight aqueous solution oftetramethylammonium hydroxide (TMAH), wherein the development time wasvaried from 5 to 60 seconds. Then, the resist was washed for 30 secondswith pure water, followed by drying by shaking.

[Defect]

Subsequently, a surface defect inspection device KLA2371 (a productname) manufactured by KLA Tencor Corporation was used to observe thesurface of the abovementioned resist pattern, to thereby determine thenumber of defects on the surface of resist portions (unexposed portions)within the substrate. With respect to the number of defects describedabove, those compositions with not more than 1,000 defects wereevaluated as “A”, those compositions with 1,001 to 10,000 defects wereevaluated as “B”, and those compositions with 10,001 or more defectswere evaluated as “C”. The results are shown in Table 5.

TABLE 5 Development time 5 sec 10 sec 20 sec 30 sec 60 sec Comp. Ex. 2 CC C B A Comp. Ex. 5 C C C B A Ex. 1 C B A A A Ex. 9 C B A A A Ex. 14 C BA A A

As is evident from the above results shown in Table 5, the resist filmformed using the resist composition of Example 14 which included thefluorine-containing polymeric compound according to the presentinvention exhibited an excellent effect of reducing defects especiallyin a short-time development, as compared to the resist film formed usingthe resist composition of Comparative Example 5 which did not includethe fluorine-containing polymeric compound.

From the results shown above, it was confirmed that thefluorine-containing polymeric compound of the present invention isuseful as an additive for an immersion exposure resist composition, andalso useful as an additive for improving defects.

While preferred embodiments of the invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

What is claimed is:
 1. An additive for a resist composition, comprising:a fluorine-containing polymeric compound comprising a structural unit(f1) represented by general formula (f1-1-1) or (f1-1-2) shown below asa block copolymer portion and at least one structural unit selected fromthe group consisting of a structural unit (a0) represented by generalformula (a0-1) shown below, a structural unit (a1) derived from anacrylate ester containing an acid dissociable, dissolution inhibitinggroup, a structural unit (a2) derived from an acrylate ester containinga lactone-containing cyclic group, a structural unit (a3) represented byany one of formulae (a3-1) to (a3-3) shown below, a structural unit (a4)represented by any one of formulae (a4-1) to (a3-5) shown below, and astructural unit represented by general formula (a5-1) shown below:

wherein each R independently represents a hydrogen atom, an alkyl groupof 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbonatoms; X represents a linear or branched alkylene group or a linear orbranched fluorinated alkylene group; A_(aryl) represents a divalentaromatic group which may have a substituent; X⁰¹ represents a divalentlinking group which may have a substituent; and R² represents a grouprepresented by general formula (III-1) or (III-2) shown below:

wherein R⁴¹′ represents an unsubstituted alkylene group of 1 to 9 carbonatoms, and R⁴²′ represents a fluorinated alkyl group of 1 to 9 carbonatoms, provided that the total number of carbon atoms of R⁴¹′ and R⁴²′is no more than 10; each of R⁷¹ to R⁷³ independently represents a linearalkyl group of 1 to 5 carbon atoms, with the provision that at least oneof R⁷¹ to R⁷³ represents an alkyl group having a fluorine atom,

wherein R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; R⁰²represents a divalent group; and R⁰³ represents a cyclic groupcontaining an —SO₂— group within the ring skeleton thereof,

wherein R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; j is aninteger of 1 to 3; k is an integer of 1 to 3; t′ is an integer of 1 to3; 1 is an integer of 1 to 5; and s is an integer of 1 to 3,

wherein R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms, and

wherein R represents a hydrogen atom, an alkyl group of 1 to 5 carbonatoms or a halogenated alkyl group of 1 to 5 carbon atoms; and R⁸⁸represents a divalent aliphatic hydrocarbon group of 2 to 12 carbonatoms which may have an oxygen atom.